Since buying a Mac I've been puzzled as to why people pay up for .Mac or now MobileMe other than to join a fan club.
I don't want a .mac or .me email address; and I don't want to use iMail as Gmail is much better - even better you don't have to worry about sync issues when it stays in the cloud, so you don't need the sync service for your email either that .me offers!
As for iDisk, lots of others offer online storage solutions, I bet many better than iDisk and what's wrong with just FTPing to a server that you have space on.
The only other benefit is to sync your contacts because you think paying for this service is easy than putting the iPhone into the cradle to sync it!
Please do let me know if I am missing something, but I only see the service is a way of saying "Steve, I pay homage to you, here is some cash to prove it".
For most people it is the sync services. Until recently, I had three macs (now only two). I need all the mail, passwords, contacts, and bookmarks to be available on all of them and I want it to work without me having to do anything. .mac does this for about $2 a week, which is less than the price of a good cup of coffee. I also use Back to My Mac to access my work machine when I am at home (this feature has already saved me about a day's work).
I also host the sites for my courses on .mac. iWeb makes them easy to manage and I've never had a problem with downtime.
Oddly enough, a couple of months ago, I said that Apple should do push email with .mac.
It's a whole new ballgame now. I have been using my iPod Touch as a PDA for a few months. Mobile Me and the app store look like turning a useful gadget into my most important possession.
The one thing they need to do is allow for the syncing of notes and to dos between Leopard Mail and the Touch.