I too have Windows 7 and Leopard dual boot on my netbook, and I must say Windows 7 is very impressive. However, in my case, it will not replace my Mac.
Additional to the coolness and virus-free factor, a main advantage of using Mac is INTEGRATION - the computer hardware, the entire OS, iLife (iPhoto, iWeb), iTunes (iPod and iPhone), iCal, mobileme (for integration and sync multiple computer, file sharing and remote access) - all from Apple.
While no integration is 100% seamless, you won't have to deal with multiple vendors for incompatibility.