Ethel -- I'm sorry, but that's simply not true.
"there are just a lot less of them out there" is what every Microsoft fan says. Mac OS X _is_ more secure than Windows XP (and in several ways, Windows Vista). Same goes for freeBSD, and various distributions of GNU/Linux. When you use other systems, you realise how rubbish Windows is at security.
Back to topic:
Mac OS X is very good at detecting hardware and working it fine. Your printer, mouse, whatever, will likely work straight away with no issues. If there are, you can visit the manufacturer's site and download the latest installer, and it'll work. Occasionally, there is some obscure hardware that doesn't work. I've never heard about any though, really.
Files -- you can get equivalent programs that work on the Mac to open your files. For example, Microsoft sell a version of their Office suite for the Mac. This'll open your powerpoint files, Word, Excel, etc. Note that you can't use any of your old Windows software. Macs run Mac OS X, and the programs themselves are totally incompatible. However, the files that these programs create can almost always be opened on other platforms, including the Mac.
*** This is very important. To solve this problem -- what programs do you use? If there are equal or very similar progams available on the Mac, then you'll be fine. But there are some programs that there is no equivalent of on the Mac. Sage Accounting systems for example are Windows-only. Macs can't open those files.
If you can, goto your nearest Apple store and try out the various Macs. An iMac may be great, but something else may fit your need.
Also note that since the software and hardware are more combined, you can get support far more easily. apple.com/support is brilliant, and there is no Windows equal.