Deal breaker: no subscribed calendars in MobileMe
I initially avoided MobileMe's iPhone syncing after following the rash of problems the service was experiencing. After growing tired of syncing my iPhone with Apple's stupid, proprietary 30-pin cable, I finally switched to to MobileMe syncing last month. It worked quite well and I was excited about it – until I noticed that my wife's calendar wasn't syncing.
It turns out that I forgot that Apple dropped subscribed calendar support in MobileMe back in August, making it a deal breaker for me. Knowledgebase Article TS1213 states:
When syncing subscription calendars between a Mac and an iPhone/iPod touch wirelessly via MobileMe Sync: Subscription calendars do not appear in your iPhone/iPod touch.
So now I'm back to syncing an advanced wireless devices with three built-in radios with a $19 cable.