Two issues that I am seeing with the current build:
1) Handheld cache is not actually caching any files with the default directory rule ([artist]\[album]) settings. It creates the folders, but they are empty. I have two handhelds set up, one uses the default directory rule settings, the other's directory rule is blank. The blank one actually creates the cache files, the 'default' one does not.
2) The settings are user specific (as opposed to library specific), and when 'changing' another users settings to match the rest - it blows away the cache directory. This is unexpected and annoying. You have to first move all the cache files to another place, then go in one by one and adjust each users settings to match the rest, then move the cached files back. Otherwise you lose them all and MC has to re-build.