I don't know if cost is an issue for you or not (and if it is, this may not necessarily be the way to go), but I switched to a Mac exactly a year ago and haven't looked back.
I used to run Windows but was always searching for the perfect Linux OS. Ubuntu was the closest I came to finding a viable alternative, but it just wasn't quite right. I had an iPod at the time and through that, discovered Mac OS X at the Apple store.
At the core, Mac OS X is UNIX. It has all of the power, functionality, security, etc. of UNIX. However, the difference is everything is beautiful and it just works. To me, it's like the perfect "Linux OS" that I was looking for.
There are beautiful applications to use. However, since it's UNIX at the core, many things can be done at the command line.
For example, if there's a software patch out, when I log into my Mac it will prompt me through a nice GUI interface to download and install. However, if I'm at work, I can remotely connect to my Mac and kickoff the software update from the command line.
One of my initial fears was that software would be hard to come by. I quickly found that I was wrong. There is a perception that there isn't much software available for the Mac but it isn't true. Maybe with gaming software, but not for everything else. I have not had a problem finding software for anything I need to do. Plus, there are Mac versions of popular software such as Quicken, Microsoft Office, TurboTax, etc.
Before I made the switch, I had heard all of the hype about Macs and the Mac OS and I thought it was just hype. I've now seen that the hype really is valid. No need to worry about viruses or spyware or any of that stuff. Not to say that couldn't change in the future, but for now at least it's not an issue. Everything is just rock solid, everything just works.
The only two limitations I see with a Mac are cost and gaming software. If you're not a computer gamer, then that's not an issue. You can buy a Mac Mini for $499 and use your existing monitor, keyboard, and mouse. Certainly not the cheapest, but I've found that it's worth it so many times over.
Mac Mini -
http://www.apple.com/macmini/
Mac OS X -
http://www.apple.com/macosx/
Okay, I'll get off my soap box now. Carry on...