Wow, I can't believe I just now discovered this. It's easy - no-brainer easy - to sync your iCal, Contacts, Mail (all accounts & rules), Keychains, and Safari Bookmarks across multiple computers.
Let me back up. I've worked on multiple computers for years. I've always had the problem of certain info living on a desktop computer at home, and different info on my laptop. Email was the worst. Getting mail on both and leaving/deleting from the server from the other is far to cumbersome with any significant mail volume. Back in my PC days, I was never able to get iMap to work for email. I tried numerous times, as did our netops guy, all to no avail. For awhile I was fine using GoToMyPC, which essentially let me work on my desktop remotely from any other computer, even a Mac. (Sadly, they don't have a client for accessing a Mac, but I highly recommend it to all you PC folks).
Then I switched back to Mac. No more remote access. Vine Server is simply too unreliable for me. I guess I've been afraid to try iMap on the Mac - I just didn't want to go through what I went through in the past trying to get it to work. I keep running up against the fact that despite several months back in the Mac world, I still don't expect things on my computer to work as they should. I bumped up against this the other day when I had messed up my font folder. I called several Mac nerd companies looking for immediate help. Finally one of them said "Have you called Apple?". Doh! I simply am not used to thinking that the makers of my system software are available to help me. I even have an AppleCare plan and I still forgot. I called. They fixed my problem in 5 minutes.
But back to iMap. I went upstairs. First I tried to change my existing mailboxes to iMap. No go - I had to set up new mailboxes. I did so. It worked. I came out to my patio and did the same thing. It worked. Then I discovered the little option at the bottom of the mail preferences window: Synchronize with other computers using .Mac. I did so. It worked. I ran back upstairs and did the same thing. It worked!
There was one surprisingly cryptic dialog message along the way - I got this for several sync operations. I was really surprised - I rarely encounter poorly-written dialog boxes in Mac software. Or am I being blinded by the light?
30 minutes after deciding to tackle iMap, I not only can now get my mail on either computer without losing it on the other, I have access to all my appointments and contacts, so I can sync with my Treo (using The Missing Sync) while I'm out of town :)
I'm having one of those "I'm so glad to be back on a Mac" days.