I agree regarding Linux... Lack of Photoshop, Illustrator, etc keeps Linux distributions from being a real possibility when it comes to being my main OS. Yeah I know, Linux has GIMP, Inkscape, etc, etc, blah blah blah. However, they aren't real alternatives to their commercial counterparts yet... not only are they missing features, but their interfaces were quite obviously designed by programmers and not UI designers, which means less-than-ideal usability.
Which leads me to my next point and my next major beef about Linux: nobody seems to agree on a single good set of standards for designing Linux software UIs. EVERYBODY does their own thing which leads to inconsistencies from one application to another (for instance, Ctrl-C is highly standardized to perform the action "Copy", right? NOPE! In some programs, it's Alt-C!). This is worsened by the plethora of different UI libraries used. The result is a horribly amateur looking patchwork of programs that would drive UI designers and less technically-inclined users absolutely insane. Hell, it's frustrating to me and I've been using computers of several different platforms for 15 years now.
And while I personally don't mind commandline use (I use the terminal all the time on OS X), it's something that scares normal users. To them, it's something they've seen in all those terrible computer movies, usually used by "hackers". It's an strange and arcane being that they're now being told to use if they want to install a driver or fix some problem and it's intimidating.
All of these factors handicap Linux's growth in the desktop market. The day that its software gains commercial-grade capabilities, its software gets consistent as possible with clean, sensible, usable UIs, and commandline use becomes entirely unnecessary (but still present if called for) for any and all common tasks is the day it will start gaining major traction with everyday normal users.