I tried posting this the other night and had some problems.
I use Linux all the time. I worked at a place that converted all of our software from AIX to Linux, there were only a couple of WinBlows machines in the place. It is a great OS, its stable, secure and fast. I get 25% faster downloads with Linux than with WD.
Also, if there is a program you like you can almost always find a free version of it out there for Linux. They have a photo editor that is just as powerful as Adobe and a money program just as good as Quicken.
I will say this though, it is not for beginners. It is for people that understand computers and better yet have used UNIX before. If you think you are just going to play and have an easy time, you won't, you will want to pick up a good reference book to follow just in case.
The latest Red Hat is really good and the 2.4 kernel is very fast and does a lot in the way of security.
Do you have any specific questions? I have been using it for a few years and would be glad to answer any.
Right now I am running Red Hat 7.1, I am really comfortable with it. Mandrake used to be the easiest to install, I would say Red Hat is on par now. There are so many Red Hat users that it makes finding help somewhere a lot easier.
They are all based on the same core and can be overlayed with the same desktops, install and additional features are the difference at this point. SuSe is out there, they have closed up their US operations so the use in the States is a lot less now. If you decided to try it for the first time I would pick up a book like Red Hat 7 unleashed or Running Linux. Something that is a good reference point.
As for programs, most Unix programs have a Linux build at this point. There are differences in Unix/Linux, and even the different platforms of each. So a program for Red Hat is compiled on RH, one for Solaris is compiled on a Sun box, etc.