I can vouch for loteq's statement. My productivity has shot up 30%. I have a medical/nursing consulting business, so you could say it's a"non-creative" business.
Anyway, when I shifted over to Mac I downloaded virtualbox and ran quickbooks 2008. It worked in the interim, however I ended up just getting QB for Mac and haven't really been disappointed. I picked up MS Office 2008 media edition on special for $100 and some change. It hasn't failed me thus far and just about everyone I consult for has a PC, and there haven't been any formatting issues with documents.
I really love some of the third party apps that help me streamline things for little to no money. I've also been able to build a few websites and tweak a few pieces of media for my business, which I had a really tough time doing on the PC, or had to pay a significant amount of money for the software to do it myself. I use Logmein to jump onto PC's all of the time without issues (I do some PC troubleshooting from time to time).
At this point I probably fire up Virtualbox 1-2 times a quarter if that, but it works well IF I actually need it. At this point I wouldn't run my business on a PC unless I was forced in some way, but I don't know what that would be.
Anyway, I don't know if this helps, but my business doesn't really fit the stereotype (photo, video, music, etc.) and I've really enjoyed working on a Mac.