A year ago I would have agreed that Ubuntu was poised to take up the slack that a lackluster Windows 8 launch would create. Now they just come off as another vendor trying to copy the success of the iPad. As a person who used Ubuntu as his primary desktop for development, I've had to move to another distro (Lubuntu) because Unity/Gnome 3 actively enrages me. I'm not saying that to be dramatic, either. Every time I've tried to use that thing I feel like I have to wash it off my hands. I realize that this might not be as big of a deal to a completely new computer user, but how many of those are really left?
As an aside (and I don't mean this to start a flamewar) Gimp is not a suitable replacement for Photoshop. Gimp has all the same functions as photoshop (and some more, in fact) but that user interface is so bad that it's not really a viable replacement. Sure, there are plenty of people who disagree with me, but I think you'll find most of them are engineers and not people who work with images for a living.
If you don't believe me, look at what happens when Adobe itself makes the slightest change to any of its products. Its user base is immediately infuriated and threatens to revolt.
EDIT: Fixed typo.