One of my favorite features of MobileMe (and DotMac before it) is subscribed calendars. This feature allows my wife and I to maintain separate calendars which we share with each other by subscribing to each others calendar. It's great way to keep schedules in order and to prevent double booking events – but it doesn't work with 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.
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.