Well, Toast can't handle all image files. And there are a bunch of burning tools that just work with windows. And for firewire:
there are not only hard-drives and CD-RWs that you can plug to the firewire-port. My webcam (firewire) can't be used in VPC. There was a wonderful chat-tool (eyeball) that was another reason for me to use VPC since it was windoze only. Well, I had to buy a usb webcam because of this.. And last but not least built-in bluetooth adapters... they can't be used as well. And there are many ppl that need their cell phones to be connected to the comp, but the software just works on windoze.
Of course, some ppl don't need that stuff and the only thing they gotta deal with is the speed. Just wanted to show there might be some ppl with different expectations beside speed.