I particularly liked the idea of having my address book and calendars synchronised and online, able to be used with the web mail. All the other features (iDisk, keychain synch etc) were all "nice to haves" but not "need to haves".
Unfortunately, the mail app failed me miserably. It was just a lot less usable than gmail. I gave it a really good try, I really did. I even hoped that the change from .mac to mobile me might improve things, but I was disappointed.
These are the things that I considered deal breakers:
- No filters: Even though the Mail interface is much like mail.app (which is great as an aside), it is missing some critical features. Filters being one of them. I like to have my email filtered into its folders (labels under gmail) automatically. To have that happen with mobileme mail, I need to leave my mac on and mail.app open. That's just silly. With gmail, I don't even need to set up the filters in mail.app, because they are filtered at the server level.
- No indication of unread messsages: You can't just look at the folder list and see which folders have messages to read. I needed to click on each one to find my messages.
- No "all unread" option: Under gmail, I can search for "is: unread". In mail.app, I have a smart mailbox set up. Nothing like that in the web mail.
Having said that, since I have swapped back to gmail, I have managed to work my way around those problems. Perhaps google have improved their IMAP implementation a bit since I last tried, but I am perfectly happy with my desktop and web mail now, thanks to Google Apps For Domains and Apple's mail.app. It is just disappointing that Apple couldn't get their webmail right.