As a daily Linux user, there is only one thing that Linux lacks compared to Win or Mac, that is third party software support. That is it, I can't go and buy (which I would gladly do, for the correct tools) software package X that works across Win/Mac/Linux.
I hope the advent of Steam on Linux causes software developers to take Linux seriously, I purchased the first Humble Bundle, and I have watched all the others, no time for gaming anymore....but I notice that Linux usually sells about the same numbers as Mac and always has the highest per unit sale price.
Occasionally (1-2 Weeks a year, when our regular CAD guy is swamped) I have to so some 2D CAD work, two years ago I was running AutoCAD 2006 in a VM on my Linux box, then this year I found DraftSight, I can't tell you how pleasant it is to use native software compared to some other solution that you cobble together just to get the job done. If I had to do CAD more often I would gladly pay for the full version to get the scripting API's.
Most Linux users are not so purist that they wont pay for software at all, given the right tools for the job they are doing they will pay for commercial software.