I'm an engineer/grad student, so functionality beats form. At the same time, I do enjoy a good looking machine.
The unibody enclosure is durable, light, doesn't flex when you pick it up by the corner, is ridgid, and has less parts than other laptops. This was one of the main reasons I picked one up. The screen is LED backlit, which gives better color and uses less battery. I've got the latest 13" MBP, 2.4 GHz and Nvidia 320m, and I run both Windows 7 and OS X on this machine. It runs both well, and handles most of my engineering applications and games. The battery life is great, and I can get all of this performance in a package that is less than 1" thick. Not many laptops offer that.
I'm pretty OS-agnostic, I use both equally, and Lenovo makes good machines. Mac portables offer both form and functionality (unlike some of Apple's other products).
The only thing that I do not like is that Windows support on the Mac is atrocious. The drivers aren't the best, which leads to poor battery life on Windows. Clearly, Mac OS is optimized for the hardware, I just wish that Windows would be as well. Sometimes I prefer Windows.