Self-built, overclocked Core 2 Duo (E6600) PC with a Dell IPS 24" panel. Built almost 4 years ago, runs dead silent, still rock solid and feels fast. No issues. Since installing Windows 7 right after its release, I've literally NEVER had to reboot or shut down the machine (it occasionally reboots itself to apply updates). I had originally planned to build another PC earlier this year, but this one is running so well, I figured I'd keep it and add something a little different and more portable - a MBP!
I love my 15" MacBook Pro i7 - my first Mac and nobody makes laptops like Apple. There are times when I just want to work on a nice full-size keyboard with a number pad, a proper mouse, and that beautiful 24" screen, and my PC works great for those times, but now, about 75% of the time, I'm on the MBP, even if I'm stationary, and that says a lot.