Since I feature both Mac and Windows plug-ins on my
website, I need to run both platforms. I do this on Mac hardware, using both Parallels AND Boot Camp options on the same machine. I recommend this Intel Mac approach to anyone, Mac or PC users, since you can run everything you need to--apps and OS's--on a single machine.
I started my dual-booting experiences on Intel hardware with Parallels and it works great (Windows in its own window, or full-screen). I recently installed Windows Vista RC1 under Parallels and it too works fine. I used to use Virtual PC on older Macs; it worked in a similar manner but was quite slow.
Only recently did I try Boot Camp (I guess I was put off by the necessity of rebooting into Windows), but it's completely tolerable. I move my finished example images over to a Mac running OS-X (using a thumb drive) for further processing or to add to my ezine layout. I suppose I could do more while in Windows, but if an app runs on the Mac, I'll use it there since (IMO) the workflow is more fluid.
I recently started using PaintShop Pro X1 and have been impressed (I normally use Photoshop CS2). I use it to run plug-ins such as Richard Rosenman's and Redfield's, which are all great, but aren't available for Mac.
Alain mentioned viruses. True, I haven't seen one on the Mac since about 1998, and it was only a minor annoyance (the AutoStart virus, which took advantage of a CD's auto-play option). I don't think it did any harm though (I manage Mac computer labs in higher ed, BTW). When I use Windows, I routinely run the Windows updater to catch any new patches (some came out yesterday). It's a productivity killer--maybe people will get fed up with this Windows way of life someday!
I've used computers since the mid-'80s (DOS) and Macs since about 1992, and I honestly can't say I would recognize a virus unless someone can tell me what happens when you get one! I've never had one shut me down (only recently have I been using Windows productively for any length of time, so my time is coming, I guess!).
PS: Tech Tool Pro 4.5.1 (Mac) is offered on a Universal boot DVD. It fixes directories, optimizes, etc. I choose to run it off of a smaller hard drive partition, of from a bootable Firewire drive rather than the DVD, if possible (faster and more convenient).
It's late and I'm rambling... ;-)