Well Astro, a good limitation/weakness for enhanced speed would also be enhanced blood loss speed. Though apparently average human speed is 8 (The internet is unreliable), so he would be 24 MPH fast. Millisecond is a thousandth of a second, so 71.125 milliseconds equal something like... 0.071 seconds. I'm not good at math, but anyway you slice Supes' build he has quite an advantage.
EDIT: To explain why he would have quite an advantage. The first, he can see, move, and react three times better than any normal human. The Strength Level system says if we're sub-human, human, or superhuman in physical abilities. Most of us are Neutral/Good/Borderline. 3 is average human strength. The only guy who so far has anything past 4 is another villain (6). Speed equals force, so he can hit three times harder than a normal human. He would also, by extension of super speed, have the following: Friction Immunity, Material Invulnerability (Extend invulnerability to materials so they don't get damaged/incinerated by the speed), a double-edged jump trick... Actually this would be a lot simpler.
Super Speed - These characters are somehow immune to the effects of friction - specifically, the chafing that would naturally occur from using extremely rapid speed for extended periods of time, especially while wearing spandex. Again, this is only for characters that aren't explicitly described as Nigh Invulnerable; presumably, that would also cover friction damage. The same applies to the materials in contact with speedster, especially clothes (that should be bent to move): either invulnerability is extended to them or they are going to be damaged and possibly disintegrated/incinerated* that probably explains why Sonic the Hedgehog is a Half-Dressed Cartoon Animal. For instance, the various speedsters of the The DCU related to The Flash each have a thin invisible aura that protects their bodies from air friction (and, presumably, the impact of their feet hitting the ground at several hundred miles per hour several hundred times per second). This aura also allows them to survive the rigors of outer space.
And they face a problem the other direction, of having too little friction. Feet coming down at superspeed would presumably have super impact, and push them off the ground and at least a few feet in the air. Even once that's explained, someone going at superspeed over the slightest hill, or up stairs, or just random dips in the ground, would lose contact with the ground, they would keep going in the 'same direction' as before, into the air. * Some Super Speedsters, like Sonic the Hedgehog, like taking advantage of this trick to reach places they wouldn't be able to get to otherwise. The faster ones would be launched into orbit, especially while doing the 'run around the world' trick. They have to have something that holds them in contact with the ground better than gravity if they don't want to end up hurtling comically though the air every other step like a Wuxia character.
Speedsters also must possess a very powerful and efficient metabolism, which keeps them from needing to drink several times their weight in pure nectar every day (In recent years, this element has been often used to justify faster healing). Sometimes, this is partly averted - more than one character like this has been shown to be a Big Eater to power their abilities - though not even spending 24/7 in front of an all-you-can-eat ice cream and candy buffet could provide enough calories to power more than a second or two of supersonic running speeds. Which means that every Speedster really is a PerpetuumMobile. Also, they have to have a very high stamina, as running from New York to Los Angeles all at once should be impossible no matter how fast they do it. They also have to have super friction powers (again with the friction), so that they can actually keep their footing when turning on surfaces that aren't specially constructed for high-speed travel. Cars turn easily at sixty miles per hour on (properly angled) asphalt, but they'd have a much harder time on tile.
And if their speed is too high for a given viscosity, there's no time for collisions to be resolved quietly, so normally soft substances (like water or plastics) are going to behave like hard ones: literal blades of grass, glass puddles, buckshot raindrops, shrapnel snow, fragile clothes, that sort of thing. Speedsters who pick up or put down anything while speeding also have to have some power that cushions the impact. Otherwise, attempting to grab a person when you're running at a hundred miles an hour wouldn't pick them up, it would snap them in half.
If these characters approach the speed of light, they would experience time dilation. Furthermore, speedsters never get specks of dust caught in their eyes...
They would also need some type of super-concentration. Given that they must have some form of Super Reflexes so they can react normally to things at super-speed, they should perceive normal speed to be horrifyingly slow. Imagine trying to hold a conversation with people who take several hours to speak a single word. Similarly, if a speedster does something like typing millions of password combinations into a computer, he must somehow avoid getting bored after the first few hundred. Or they may have nervous systems that can multitask at different speeds, allowing them to perform (for example) simple manual tasks at superspeed while only being consciously aware of a few seconds passing.
Characters with super speed must also be able to withstand massive g-forces caused by rapid acceleration/deceleration, since most of them are shown to be able to start/stop instantly (rarely applies to those who lack this talent, but they may end up going Too Fast to Stop as a result and find that Inertia Is a Harsh Mistress). This must make the character somehow able to anchor to the ground while stopping too, since friction with the ground can only go so far - but often they just instantly stop. More than likely this uses some form of Inertial Dampening rather than actual friction, as it normally fails to tear up the roadway or set it on fire.
Normal humans moving at very high speeds without a protective barrier would forcibly ram-scoop air into their lungs. It'd be like driving without a windshield... on a supersonic jet. So their "aura" must either slow the air, or redirect it safely around them (while still allowing in enough to breathe). There was a real life incident where the navigator in a US Navy KA-6 Tanker ended up hanging out the cockpit of the aircraft. His seat had become detached from the floor due to metal fatigue and ended up pretty much floating on the ejection guide rails. His helmet and oxygen mask were taken off by the wind. Through his apparently being one of the luckiest guys in the world, he survived, and later compared trying to breathe during the ordeal to trying to drink from a firehose. This on a subsonic aircraft with the pilot deliberately flying as slowly as he could (unlike most vehicles, aircraft stall when they fly below a certain speed due to the lack of lift).
Also traveling at very high speed would generate shock waves that even if they won't affect the speedster would affect everyone around.
And in the cases of extremely high speed, there is also the risk of the radiation (principally Gamma Rays) produced by the Doppler Effect of traveling a such high speeds.
You could probably take a reality-based view regarding his super-vision though.
quote: No, exact words don't apply here Liam/Supes. So, let me actually explain the implications of his combo.
The ability to selectively screen your input is an absolute necessity unless you want your hero to be called "Captain Migraine", "The Squinter" or "Curled-Up-In-The-Fetal-Position-On-The-Floor-Man
Heroes with this power also seem to automatically gain the skills needed to properly interpret the new sensory input. In reality people tend to struggle when they suddenly gain a new sense, and it can take years to adjust to it.
He moves and reacts at three times human speed, with three times greater sight. The faster something moves, the more force involved when it crashes. Being a practical person, Supes would know simply dodging bullets would be smarter than trying to grab one. Since he can see further than any normal human, he would be able to make out details better. So, coupled with his reflexes/speed and sight he can quite effectively dodge any human-scale/lesser-scaled enemy. Plus, give him a knife and he's quite good at killing people. Since the main enemies are human S.W.A.T, he shouldn't have much difficultly in avoiding/killing them. Though, any weaknesses to all this would just sort of horribly end badly for him if something went wrong.
< Message edited by kkutwar -- 4/17/2012 19:48:14 >