I think that it's mostly just about OS specific applications, games in particular. For example, video editing software like Final Cut is made for the mac os. However, with stuff like that there is likely a fairly decent equivalent in Linux (I don't know if it has all of the same features, but it will probably get the job done). So really the big thing is probably games.
I could also see something like a Windows 8 Metro style menu not existing on Linux, but I feel like that's more about not having as much community support for it and less about whether it is actually doable by the community
Personally I havent had the time to sit down and really learn the linux version on computer at the moment so right now it's collecting dust in the state I left it in on my hard drive after setting things up. But I was able to find equivalents (and in some cases the exact same stuff) for just about all the software I had on Windows, minus games