The new BusyCal public beta allows you to sync with the new MobileMe calendar beta and other CalDAV servers. It also includes the ability to sync over your local area network and Google calendar. I’ve been running it since last week with no troubles. I think, in the end, the transition to CalDAV is going to benefit everyone.
Why would we need busy cal with new mobile me sync? I got busy cal to sync my calendar with my wife.