I installed this on my Sansa e250 MP3 player a few weeks ago. So far, I'm extremely impressed.

I did it to fight several annoying problems with the original firmware, lousy fast-forwarding being the main target. It's fine for songs to FF 5 seconds or so at a time, but it's horrible when I've got a 1 hr+ podcast and it gets interrupted because I've hit the (stupidly placed) record key, or just forgot and left it paused till it turned itself off. Taking 5 minutes or more to get back to where I was is not acceptable.

It also kept deciding that it needed to re-scan the add-on memory card for music to add to its database every time it booted up. This process was slow as hell, taking several minutes each time. Ugh.

I remember someone mentioning Rockbox on GWJ once before, and thought I'd look into seeing if it could fix the problem. After using the Rockbox utility to auto-install, then manually scanning for entries in the music database, it was ready to go.

The whole interface just feels better to me. Power button always goes back, wheel click always selects, etc., rather than the contextual menu system that made it impossible to navigate around without looking at the screen.

Not only will it keep increasing the FF/Rewind speed as long as the keys are held down, it also doesn't force me to go back to the menu each time I want to do so. I've actually needed that feature a lot less than I previously did, as it automatically bookmarks songs so that I can resume playing from the spot it left off.

They even managed to fit games into the Sansa. Games! There's an Arkanoid clone, Space Invaders, even Doom (if you have the original WAD). Dozens of 'em, each at least as good as the kinds of games people play on their cell phones.

It has several other improvements over original firmware, though most are geared towards the audiophile crowd. If you've got a compatible MP3 player (currently a hodgepodge of iPods, Archos, Conwon, iRiver, Olympus, Sandisk, and Toshibas), I can't recommend Rockbox enough.