So, I decided to try out
MobileMe to try to keep my calendars and contacts in sync between my three computers (two Mac, one Windows) and my iPhone. So far it's been quite aggravating.
At the core of it, the primary problem is just that the computers all do pull-based sync, and they don't do a very good job of handling contention. The Mac clients just spinlock forever waiting for the others to complete, and the Windows client puts up a very annoying dialog box right in the middle of the screen telling me I "can't sync now" because another computer is trying to sync. This happens about every 15 minutes, and there is no option to suppress it.
Meanwhile, the reason I decided to try this is because I finally got sick of Plaxo's less-than-stellar capabilities (its Outlook sync is merely tolerable, there's no direct iPhone sync, and it doesn't preserve alerts when syncing calendar events so the whole point to syncing my calendars goes out the window anyway).
I suppose I could just switch to syncing all my computers manually for now until Apple gets its collective head out of its butt regarding user experience. Argh.
(Of course if this were a true push solution it wouldn't be a problem — the only contention issue is while a client is pushing an update up to the server, and that's not likely to happen simultaneously. In the rare event that it does, the second one can just wait.)