In OS X 10.5's QuickTime Player, it was easy to control how quickly you could fast-forward or rewind a playing movie. There were two ways to do this. Select Window -> Show A/V Controls, and you could then use the Jog Shuttle and Playback Speed features to control your movie's playback speed.
In Snow Leopard's QuickTime X, the A/V Control palette has gone missing (along with any number of additional user-friendly features). In its place, we have just the Fast Forward and Rewind buttons. Click once, and the speed changes to 2x; click again for 4x and then 8x. While this works, it's not nearly as flexible as the options offered in the A/V Control palette in Leopard -- or at least, so it seems.
As discovered by Mac OS X Hints contributer ipearx, you can get better control over the fast-forward and rewind speeds. The secret is to hold down the Option key before clicking either the Fast Forward or Rewind button. With the Option key held down, the first speed you'll see will be 1.1x, and each subsequent click will increase the rate by .1x, up to a maximum of 8x.
While still not as flexible as the Leopard version -- there's no job/shuttle controller, for instance -- it's nice to have more control over playback speed. I've found I can watch a video at somewhere around 1.2x to 1.4x and still follow all the audio and video.