Today I ran into a MobileMe file sync problem. The most current version of a file was "stuck" on my MacBook. I couldn't get it to sync to the server. I got a cryptic sync error message, but nothing else.
Eventually MobileMe put up the dialog I was expecting, asking me to resolve a sync conflict.
I'm not impressed. I haven't asked much of MobileMe, but it's already failed me.
I'm going to give DropBox a try -- and keep looking for some other way to manage my address book. I'm hoping I'll be able to drop MobileMe after this year is up.