lindsay, evan is spot-on with debug mode. reset dumps your local cache and all connection information. it should only be used in case of a serious problem.
sorry I can't spend more time here, but the community at macrumors is very awesome, and we really appreciate the support. a little more troubleshooting advice:
-if you are getting songs on the iPhone and things are playing back, you should ignore debug and Reset settings.
-if songs or playlists are missing, the most likely case is that, either they haven't been scanned yet on the serving computer, or their meta information hasn't been sync'd yet on the iPhone. I know it is frustrating, but the best advice is to wait. FYI: playlists only show when the whole library is scanned / loaded
-if you are looking for your iTMS-purchased DRM-protected music, we need iTunes to play that, so it isn't shown on the iPhone.
-if you are getting no songs at all, using the Report Issue option to send us an email with diagnostics. we are a little slow on responding, but we will get back to you.
I hoping to add a much longer, more detailed FAQ to our blog tonight. And, obviously, the product will be much better when we explain to you what is actually happening during the setup phase.