I'm experiencing problems with corruption of files which have already been sync'ed, but are not being subsequently modified anywhere in any way.
These files, e.g. picture files, documents, etc., are just reported as being corrupt and cannot be opened by any app.
I'm not sure what causes it and I can't reliably reproduce the problem, but it does happen a lot. Often, I have to clear the cache and resync.
I also have a feature request which is related: provide a way to sync the entire contents of a folder and/or Dropbox. I know that there was already a feature freeze, but this would save a lot of time when I have to resync a bunch of files.