I have tried Mint, Suse and a few other distributions including Ubuntu some time ago on both live and installations. They were ok and a viable choice. I even ran OS/2 trial some years ago

I have an Open Pandora which runs Linux and can also boot to Android.
The main reason I don't use Linux on a daily basis is the need for specific apps like Vic2000 but that is true only for work.
I could switch my home PCs to Linux but there is no burning platform to do so for me...yet
Windows comes pre installed included in the cost of the Laptop - so that is inertia.
I am not so confident to dig into all the system stuff as quickly as I can in Windows or to find the help. I am more confident in DOS. Searching the forums previously was unfriendly.
I like tinkering and solving problems so will try it out again at some point, especially as I have a 2-3 year old Win 7 laptop available to play around with soon - I will see if I can build an emulator box.
In summary I think:
1. I think a lot of people use Windows due to Inertia from Mainstream availability and retail support
2. Key Programs are Windows only.
3. Linux is still not mainstream enough and there is no Killer App (for the masses)