I am loving Rockbox so far but there are a few gripes that prevent me from using it on a daily basis:
- Cant adjust volume with volume button when N900 is locked
- No configurable keys (Eg: I prefer to use space as the pause/play key and also have a dedicated key to go to the now playing screen)
- No pause when I unplug headphones
- Japanese characters are displayed as squares (Sazanami Mincho font works but font is too small to read)

I have experience in C programming and might be able to help if I have access to the source code and details on how to compile.