I forgot to add that the Apple Mobile Me support page states that you’re responsible for backing up the data on your devices (iPod touch, iPhone, and iPad) before syncing. The only way to do this is to hook them up via a USB cable and run iTunes. Not sure what the point of having a wireless syncing service is when you have to do that first.
The Apple support page also described how to retrieve your data via Time Machine (Apple’s backup system.) I don’t know how many Apple computers come with the second hard drive necessary to run this feature. Mine didn’t, so until I buy one I’m SOL.