I'm a Windows programmer by trade--I live, breathe and sweat Microsoft more than 40 hours a week. But like with any good doctor, lawyer, etc. you have you broaden your field of knowledge.
I started with Ubuntu out of curiosity. I wanted to know what the hype was all about. So, I downloaded the installation disc from the website and installed.
It was, by far, the easiest installation I've ever come across.
Everything worked off the bat--my audio, my wifi, my monitor, my bluetooth keyboard and mouse. I was on the internet using Firefox, listening to all my MP3s, watching all my videos in less than 20 minutes of downloading the installation disc.
My only gripe so far is that it doesn't support dual video cards, yet. At least from nVidia. And yes, I've gone onto the support forums and Googled the heck out of it... tons of other users are having the same problem. The issue is with nVidia, and not with Ubuntu itself.
With that said, I highly recommend Ubuntu. It's fast, safe, and uses a lot less resources than Windows. WINE will help you if you have applications that can only use Windows.
What you can do with Ubuntu: You can go on the Internet, write a document, use OpenOffice, write Lunch reviews, network with printers and other operating systems, nearly everything that isn't listed in the "what you can't do" section.
What you can't do with Ubuntu: High end gaming. .Net programming (for me). That's it!
My solution: Dual boot. Have both Windows and Ubuntu on the same computer. And guess what? You can read files from both operating systems. :)