I would not buy a Mac if I couldn't run Windows on it. As much as I want to get away from Microsoft, they are a necessary evil for work. Plus two of my favorite non-work related applications are Windows only. I almost bought a Macbook four years ago with "Virtual PC" to run my Windows applications. But Virtual PC's reviews were so bad, especially after Microsoft acquired it, that I decided to stay with Dell.
There have been several in my office the past 18 or so months that have made the switch to Macs, using Parallels to run Windows. When I saw their machines running Windows faster than the PC machines, I was hooked. So I'm eagerly awaiting the delivery of my first Mac!!!