Great question Patrick,

For me, I use Windows because I like the direction that 7 is headed in.  I enjoy Aero and applications like Rainmeter allow me to create a visually stunning desktop.  I feel like Windows caters to my sense of multitasking, but I haven't put too much effort into Ubuntu.  

You could ask the same question about why people use Photoshop over GIMP or Paint.net.  I'm already hooked into that system, my mind knows how to work it and there is no guess work.  

I'm also not a command prompt wiz kid, which I feel is an important part of getting around Ubuntu.  I'm actually glad to be rid of DOS (even though I nostalgia hard when I think about those days).  While Ubuntu is simplified enough for the average user to grasp, it lacks gaming capability (except for Steam) and it just doesn't look as pretty.  

It is MUCH safer though. (as is my understanding)

Why do you use Ubuntu when you could use TinyCore? ;)

I had to install Ubuntu (server), and I find it easy, until I have to install other packages.

If fact, it was not so complicated, but when you are minded with a desktop style manager, it's (a little) scary to go command line in an OS you don't master.

I will give a try to a desktop style Ubuntu install, and see. 

I know about Linux issues with games, but there are several you can try in Ubuntu. Besides that, the decision to change to Ubuntu was mostly curiosity, but after trying for some time I realize that a lot of the problems I used to have as natural in Windows (like errors, and slow computers after a while), disappeared completely in Ubuntu.  Yes, I found other problems, but that's another story. 

I run a business and have to be able to work with commercially available programs like Photoshop, Indesign, Excel etc. There are of course programs "like that" for Unix, but they really are not of the same quality yet.

@Robert,

"Quality" is a kind of fuzzy word. They work, they don't crash and they perform for the job.  you can do in GIMP what you can do in PS, the user interface just isn't intuitive.  I think that the mainstream operating systems definitely have more effort from developers to create programs that are better for the every day user.