Rockbox is fantastic, it offers;
- Better battery life
- Easier browsing
- Better EQ
- Gapless playback
- Games
- Way more settings to play with if you desire
- Faster database refreshes/loads with a SD card
And to top it all off if you don't like it, you can simply delete the .rockbox folder and remove it or you always have the option to boot up into the OF.
As far as bugs concerned, there is none really. People have been having great success since the more recent release of a stable port. I've been using it for a few months now and haven't had any problems.