My only issue with using a PC is (ironically) Apple software - with so many editors using Macs, Quicktime (ProRes and H264) has kind of become the defacto standard for editing and distribution. The PC's out-of-the-box codecs are CRAP and Quicktime is just bad on the PC. I've had major issues with gamma and audio sync using Quicktime H264/MP4 on the PC that just don't exist on the Mac side.
I've been toying with the idea of switching to Avid's DNxHD codec for editing but next to ProRes 4:2:2 it seems pretty lossy. If I had the choice (or rather, the money) I'd switch to a Mac for my editing purely because there seems to be less voodoo involved in getting the best output out of it.