Is it possible to play back video at double speed, but keep the pitch normal? How about playing back at a fraction of double, say, 150% speed?
No, not that I'm aware. Yes; try Shift+L (for forward play) and Shift+J (for reverse play). Start playback with L, and then tap Shift+L; that should increase speed in 25% increments, and you get a number of steps before it tops out. You can do it from a paused state, as well, and get fractional slower-than-realtime playback--that's very helpful, as well.
Thanks for the shift + L tip!
One thing I didn't note, that you might have already discovered, is that the Shift+J/Shift+L playback controls are on a sliding scale. If you're going a little too fast on playback, you can hit Shift+J to slow it down, instead of it immediately reversing.