I keep my old machine for playing with Linux. After 18 months of that, and with it booting into three different flavours of Linux or into Windows, my take is:
1. Linux is very capable, but a lot more "nerdy" than Windows, and it takes a lot of time to get everything working. By comparison, Windows is a walk in the park.
There are lots of different flavours of Linux - called "distros" by the aficionados - some are a bit like MSDOS 3.11 and require a PhD in geekery, some are nearly as user-friendly as Windows. I get on well with Debian, fairly well with Fedora, and after a fashion with SuSe. I've not tried Ubuntu, which I'm told is also nice.
Knoppix is interesting - it will run from CD or DVD: I've used it several times to recover stuff from friends' computers that have crashed or refused to boot from their hard drive.
2. Networked printers are a nightmare: they will work under Linux, but you'll spend many hours getting them to. It's a lot better for your nerves to buy a printer for each Linux machine.
3. Wireless connection is awful. I can get a Windows wireless network up and running in minutes. I've not yet managed to get even a hint of success with Linux. I can't connect any of my machines to the wireless network if I boot them in Linux. I've downloaded gigabytes of stuff that's supposed to make it all happen, but you need a D.Sc to understand the instructions.
4. Open Office is free, and competent. The Word Processor and Spreadsheet bits are fine. I've not managed to get anything that'll do what MS Publisher does. They may be "out there", but they are hiding well.
5. Debian has a wonderful feature: Kpackage - which allows you to look at a list of just about all the software available for Debian Linux, and to install or update whatever you want via a graphical interface. I love that! Much of it is super-geek, but some is excellent and very useful.
6. Linux will drive you crazy typing in the "Super User" password. If you're trying to set anything up, you'll be typing the pesky password several times a minute. You can't tell it to shut up and get on with the job - it just keeps demanding the password for each different operation you try to carry out.
7. Once you get it all working, Linux is many times faster and more efficient than Windows. It just took me about 15 months to reach that happy point - but I didn't have a local guru (I do now).
8. Asking for help on Linux forums is not for the faint hearted. Most of my requests for help resulted in me being flamed for being stupid (everyone knows how to to a ../config.-grunt-/kipper -t +R -x +z:1 or they shouldn't be allowed out alone), or for wanting to do such a silly thing as to print something, or for not asking in the approved format etc etc. In 12 months of trying, I never once got an answer that was any help on any of the forums (although I gave a few). Google helped a lot; now I have a "Linux guru" who is brilliant and either answers immediately, or finds the answer within a day or so. No, his name is NOT available - sorry!
IN SUMMARY ... would I switch to Linux for key functions? No way, without a resident and proven expert to fix it.
Would I recommend it? If you have plenty of spare time to learn a whole new way to operate your computer, and like a challenge - yes.