I have Thinkpad X220 with Xubuntu installed in it. I've been using Ubuntu for about 5 years now. I have tried different desktop environments like Gnome, KDE and Xfce. I tested Debian and Linux Mint in laptop use, but they had their problems.
Ubuntu is great but I've faced countless problems with external monitors etc.
(I wanted to try Xfce and thought that Xfce+Compiz is still lighter than Gnome+Compiz.)
I have encountered these bugs quite frequently. I code a lot and solving bugs in my own programs is enough. I want my environment to just work.
Something new had to be tried and Windows wasn't an option. I just don't like .bat, cmd.exe, C:\, and those windowsy things.
Laptop is the best choice for me because I travel a lot. So I bought 13" Macbook Air with 128GB SSD. It's light, mobile and has a decent resolution. I had also planned to test how to code an app for my iPad, so being in Apple-camp helps.
Now I'm trying to use the Macbook as my main working/coding laptop. Currently I have OS X Lion 10.7.4 installed. I don't know why I even expected anything else, but OS X needs heavy configuring to make it usable.