I, for one, enjoy previewing the nightlies when possible. It is not critical that they are stable as no real work should be done in them, but this should not stop people from at least seeing what it is capable of. If you do manage to get something useful done, huzzah!
Right now, the only thing that's important to me is that they compile and at least start OK. Since the code is undergoing a major revamp right now, stability is not the best and compilation is not always possible without manual intervention.
Watching the new features being added is also exciting. Lately, I see code sections for OMR (score scanning?), Aoleus (organ pipe ranks), OSC (remote control?), side-by-side score scan and score entry, score albums, user profiles, MP3 export, fotomode, etc. I've probably missed a few biggies.
So what features are you waiting for to be completed, or would like to see introduced?