Yep. Linux and other alternative OSes are still a tiny majority of what the majority of people use. I figure about maybe 7-10 percent of people who are active on the internet use Linux. Maybe only 2-5% of people who use computers use linux for anything. It's pretty small. The more technical circles you will find much higher Linux/BSD usage, as high as 30-40% in some types of professions.
Server markets and stuff like that Linux is getting much better. In internet servers OpenSource dominates with over 60% of web servers being Apache and the various ftp servers... This compares to about 23% or so on windows side. Of course lots of these servers are being run on BSD's and windows.. so It's still not clear how much are being run on Linux. Maybe 30-40%? And lots of the servers reported are for small-scale stuff and for mid to high level businesses generally use windows, although Linux and BSD I think are used for the highest end stuff like Google and freinds. I am gessing that maybe 20% or so of corporate servers run Linux. Of course this is generally in conjuction with windows and stuff. Lots of people who are in a corporation would think that they are in a windows only network or novell only network would be suprised to find out what is realy used. One intersting tidbit is that NT was originally designed to be a Unix-killer. People generally didn't like Unix and it was old-fasioned (when everything was system-V stuff). MS figured it would make a killing with a easy to use server running on cheap hardware, but it didn't make a dent in traditional Unix markets. People quickly found out that you would have to replace 1 unix server with 7 or so Windows servers to equal the same ability and you'd have to double or triple the workforce. However the PC explosion happened and all these PC people needed servers, but had no knowledge about Unix or anything and thats how MS's NT became so popular. However Linux is now doing what MS couldn't do.. Which is making a huge impact on Unix server markets. That's were most of Linux's growth is in, much to the detriment of companies like SCO.
Of course all this is speculation estimants widly change and swing back and forth as far as actual numbers. Traditionally server sales were what determined the estiments so people still try that with keeping Track of Redhat or Suse sales, but how to do keep track of the thousands and thousands of installs from anonymous ftp? You don't, so you have to guess.
Good thing that the average people know very little about computers, mostly using e-mail and stuff... makes it easier to switch. People done studies and it takes about the same amount of time to train people to use windows as linux. The difficult part is setting everybody up, but nowadays I using pre-installed and configured machines there is nothing realy more difficult exept with installing third party programs. If Redhat or one of those guys design a effect package managment like what Debian uses but is something a non-technical user can relate to, then Linux can actually have a edge on usability. As far as the old argument that would your grandma be able to use it.. Well she could, I have to help her clean out and fix windows problems every time I visit. Viruses are definately a problem and adding a effective virus scanner doesn't realy help matters so much. Installing a printer with drivers is a almost insermountable problem for her, much less using a restore disk and reconfiguring and reinstalling all the drivers. I don't see how it would get worse with Linux... Hell I could keep her from root and it would probably make things easier for everyone concerned.