I *just* got the 27" iMac... and oh my word, it is GORGEOUS!!!
I found that I really didn't need a laptop anymore and I wanted the stability of a desktop computer.
I've had this Mac for a few days and I think the switch has been super easy! I've been able to google a few things real quick (like how to take a screenshot) and found the answers to my questions easily. I was expecting a much harder transition, but it's been great! And this thing is screamin' fast!!!