None. I've had far more moments when I wanted to toss my MBP out a window that when I wanted to toss my PC out the window, and if someone offered me a direct trade of my MBP for a Thinkpad T60p now, it'd be a hard choice, but I'd probably take it. I just wanted to try something different, I guess. Or maybe I should say "see what current Macs are like" because I used a pre-OS X mac for a long time before I ever seriously started using PCs. I have had my Macbook Pro since March, and while it's not a bad system (OS and hardware), I don't really understand the hype. It's doing most of what I want, but I suspect when it's time for a new computer, it'll be a Windows machine again. Maybe in 3-4 years though when it's that time Macs will have gained enough market share to yield increased software availability, or something like WINE will be available, and I'll consider getting another one.