What Mike says is basically true, because of it’s market share (which, I believe, is closer to 5%) there are fewer applications written for the Mac, but …
When I was looking for an accounting package, a search gave me 130 or so for a Windows based PC and only 23 for the Mac. I was still able to find one that met my needs.
Microsoft supports the Mac. The Office suite (Excel, Word, Powerpoint, etc.) is also written for the Macintosh. Adobe Photoshop, Illustrator, GoLive, Dreamweaver is all available for the Mac. All of the documents written for these are cross compatible with Windows based machines.
Although more expensive, a Mac is much easier to use (I get annoyed when I am forced to use a PC at our library) and it is very easy to customize. The Mac OS is, if you read some of the Tech Forums, much more stable than the Windoze platform. My Mac almost never crashes, but when it does, I do not lose data!
Also, (perhaps because of its market share), the Mac seems to be much more secure. With Norton Anti-Virus installed, I have only intercepted two viruses or trojan horses in the last year and one does not need anti-spyware with a Mac. I suspect most PC users worry about becoming infected much more than I do.
If your budget allows and you want to make the paper-to-electronic transition easier, consider a Macintosh. There is a lot of support out there in cyberland.