I got the trial service and to be honest, I haven't really gotten any use out of it. I already have a ton of email addresses, so another one doesn't really do me any good. I don't use Mail since I prefer to have all my mail sitting on a single computer, so I just have Thunderbird check my messages on my PC. I use Adium with my AIM and MSN screen names, so I don't need the mac name for iChat.
Looks like you can only sync Safari bookmarks, so that doesn't do me any good when I primarily use Firefox. All the contacts I need are in my Gmail account, so no use in syncing those either. Finally, I can only use Outlook for syncing with my PDA phone, so no point in using iCal.
Overall, .Mac is a great service if you use all the programs it supports. But for a person like myself who doesn't, it doesn't hold much use for me and thus I can't justify spending a hundred bucks a year on it. Even iDisk is useless to me since there are plenty of free and not to mention bigger online storage services available.