I would suggest avoiding proprietary software entirely, if it is at all possible. Donating 10 dollars to the GIMP developers is much more worthwhile in my opinion, when you take a long-term view of things. If everyone who wanted an alternative to Photoshop did that GIMP would be better by now. (Actually, having looked at recent development builds, it is pretty damn close)
This new year I am going to become a card carrying member of the free software foundation and am making a donation of 10 dollars to the KDE project.
If everyone did that, or even less (1 dollar per person adds up if there are a million users) it could make a huge difference.