I remember a sequence in The Flash comics from only a few years ago. This would be the Wally West Flash, after the Barry Allen Flash had, um, "merged with the speed force," which is to say, died, albeit a comic book death (and they seem to be about to bring him back). He was Saving the Universe when it happened, so it would have been unseemly to bring him back too quickly.
Live fast, resurrect slow, that's Barry Allen.
Anyway, the gag, to use a movie stunt term, involved Wally West sitting in a movie theater with his girlfriend when suddenly everything freezes. Everyone is a statue; it's dead quiet, and the movie is stuck on a single frame. Wally thinks, "What the hell?" then he notices a slight pressure on the back of his neck. It's a bullet; someone has tried to shoot him, but as soon as it entered his "speed force aura" his body switched to super speed and there you are.
The speed force aura is also what keeps his clothes and skin from being burned off when he's moving really fast, and also allows him to pick things (and people) up and carry them without them also suffering death by super speed. Very useful, that speed force aura.
In Justice League Unlimited, the cartoon series, the Flash is always getting hit or even knocked unconscious by folks that really should never be able to lay a finger on him. That's a failure of writing, of course. The movie theater gag did kick it up a notch; traditionally the Flash had to "get up to speed" as it were, so there was a window of opportunity for the bad guys to get him. (Phil Foglio once told me about a character he'd invented—but has never actually used, unfortunately—called "Tube Man": very powerful but who takes several minutes to warm up). But the JLU stuff sometimes has The Flash taken out while he's running, and that's just lame. You might be able to hit him with something that moves at the speed of light, although tracking him should still be an issue, but otherwise, the whole point of the Flash is that he's faster than anyone or anything else.
The Flash can be, but usually isn't, a vehicle for philosophical ruminations on the nature of time and humanity's relationship to it. As the Jay Garrick Flash said once, the point of being The Flash is that there are always enough hours in the day. Need to learn some branch of case law? Done in fifteen minutes. Build a house? A minute and thirty seconds. Study for that calculus test? Do it while everyone else is walking to class.
But it's a lonely time there in the speed force. Apart from the occasional carrying of the fair damsel away from the exploding bomb, The Flash is doing his job in a world of statues, reminiscent of the Arthur C. Clarke story, "All the Time in the World.
There have been variations of the super speed power that had more of a downside (though none greater than the Clarke story, I think). In Wally Wood's T.H.U.N.D.E.R. Agents, the character Lightning was using up his actual lifespan while doing his super speedster act, so he was aging more rapidly than his compatriots. The same was true for those under the influence of "tempus fugit" pills in Heinlein's The Puppet Masters. (Aside: there was also an episode of the 1960 television show The Man and the Challenge that involved a drug that hyperaccelerated reaction times. I'm only scratching a trivia itch with this tidbit).
The potential for loneliness inherent in the character of The Flash is interesting, and it's also interesting to wonder if that aspect of it has influenced the way that The Flash has been incarnated over the years. There have been more versions of The Flash, more different people carrying on the tradition, than any other character in DC Comics, (excepting Green Lantern, who became part of a universe-spanning Corps). Moreover, Flash's tend to get married. I doubt that the writers were consciously making the contrast between the need for companionship and the loneliness of the Power, but the writing is often smarter than the writer, and I speak from experience.
My friend Ben Sano also notes the interesting contrast between The Flash and one of his most formidable foes, Vandal Savage. Savage is immortal (though they've screwed around with that recently, and not to the character's improvement), so he has the complementary power to The Flash: they both have all the time they need. Savage, of course, has seldom been written well; over the centuries, his tactics should depend heavily on waiting out the opposition and, perhaps, compound interest. On the other hand, part of his deal is that he is a savage, having been born something like 50,000 years ago.
The time available to either The Flash or Vandal Savage (one compressed, one extended) also allows an examination of the some of the same issues raised in some variations of Supersmart. They had essentially unlimited time for learning, but learning, per se, does not equate to intelligence, insight, or judgment. The Flash may have "lived" the equivalent of many centuries while in the speed force, but can still be socially awkward, because little of it was in interaction with other people. Vandal Savage may have lived for 50,000 years, but he's never going to stare at the equations of atomic state transitions and invent the laser. The extra time can only be spent on the things you can do, not those things you can't.
Still, there are so many possibilities that never get explored, because there are only so many hours in the day. Except for The Flash.
What, did you think this essay was going to be about femto-second laser pulses?