MobileMe is the AOL of ISPs. It's more expensive, easier and prettier. But you can get the same thing for cheaper (and in this case, almost everything for free), takes slightly more effort, and isn't as aesthetically consistent... or consistent amongst websites and programs you'd be using, etc.
I'm a MobileMe user, to have the ease of use as a "fuhgetaboutit" feature and to just use my native Apple applications is worth the money for me. But don't buy it thinking it is anything innovative. There isn't anything new to it. Very little is new in comparison to Apple's previous .Mac service and everything else has been done before elsewhere.