Its actually a really long list but the crux of the issue is games and other software that don't run there. The problem in many cases is that Linux isn't very business friendly as a platform making the drivers and commercial software harder. I like it for programming but for games and enthusiast software its kind of bad.
For programming ? It is my experience that everything that linux has, is either better, or much better on windows than whatever is available on linux.
gdb vs VS debugger ? No contest. (even if you have the crappy ddd frontend)
openGL debugging ? Again, no contest. Lots of quality software on windows, but on linux ? Ugh.
Editors ? I still find the ones available on windows is better than anything on linux that I have tried.
The main issue with linux is the terrible or non-existent support for lots of hardware that have no drivers for linux. (Yeah, I know, you can blame the makers, but still, it sucks when something works fine on windows, but won't work at all on linux, or barely works, and crashes).
There should be out of the box support for mice with multiple buttons, same with keyboards that have extra keys that you could configure.
There is no "clean" way to switch resolutions in games, they all seem to do things different, and it may or may not work with the window manager you got.
The cryptic logs and or commands also don't help a n00bie out at all.
The whole binary blob vs OS for video cards just plain sucks. If you want performance and less crashes, you use the binary blob. If you want headaches, and slower drivers, you use the OS version.
It looks like they are trying to fix most of these things with SteamOS, but, we will see how far they get.