I'm glad there's already a topic for praise of Rockbox (no doubt there are others here!).
The more I use Rockbox on my Sansa e280, the more impressed I become--and I was already very impressed when I first used Rockbox on my old Archos Recorder.
For example, the Sansa allows voice recording with surprisingly good audio quality. But in wav. No problem for Rockbox--it can be encoded on the machine into wv (lossless) or mp3. So, all one needs is enough temporary space to record in wav.
No wonder Sandisk opened up its hardware to Rockbox. I don't see how anyone could be happy with an un-Rockboxable iPod...
UPDATE: Oh of course! I just learned how to record directly to wavpack if I want (or to mp3).