My hardware:
15" MacBook Pro Retina, 2.6Ghz, 16GB DDR3
OSX 10.8, Windows 7
Dual NEC 27" Displays (PA271W-BK)
Das Keyboad (Professional)
Logitech Performance Mouse MX
I travel a lot, so a notebook works great for me. When I'm home, it is plugged into two 27" displays, and when I travel, the 15" retina is a perfect weight/size to get things done but not be a hassle. I spend half of my day in Windows, half in OS X 10.8 - I can boot into either in about 30 seconds. And I just love the 'clickiness' of the Das Keyboard - its like a high quality IBM Model M keyboard.
So HN, let's hear about your setups!