I love speedsters. If I could pick any single power in all of comics, I think it would be the Flash's version of super speed. If I couldn't have that, I'd even take Quicksilver's version. A quick note: when I say "single power," I'm talking about the speed and all the accessory powers that are necessary to make it work, like enhanced reflexes, endurance, etc. A speedster, properly written, is the only character you need on a team 90% of the time.
|Arrogance is a speedster accessory power|
|About half of the Flashes in DC comics|
And that's before you consider all of the other peripheral speedster powers. Not every one of them has these type of powers, but Flash, for example, can vibrate his molecules fast enough to pass through walls, run up walls and across water, create localized whirlwinds and updrafts to lower falling items or raise ones that are on the ground, manipulate others' kinetic energy, throw objects at near-relativistic speeds, and even travel through time or across dimensions when using his cosmic treadmill.
There are a lot of great speedster stories out there, but many of them require that the character takes it down a notch. On team books, especially, the speedster often has to be either ignored, knocked out, or in some way occupied to keep from breaking the narrative; this happened fairly often on the Justice League cartoon, according to one of the writers, simply because it was too hard to make a legitimate challenge for the Flash. When you read a team book that has a speedster in it, keep an eye on that character. You can get a good handle on how well the writer can work with superheroes by seeing how he manages the speedster.