So I've used various drawing programs for years to make crappy little graphical schematics to post online. MS Paint is all I really need, although I've used Photoshop and similar programs as well.
I heard a lot about how powerful GIMP was, and my Mac didn't come with even a basic drawing tool, so I downloaded it. Lasted... oh, maybe 2 minutes.
The issue came when I wanted to draw a line. Now, every other graphics program I've used has a "line" tool, somewhere in plain sight. Observe:
http://windows.microsoft.com/en-US/windows-vista/Using-Paint
http://www.extropia.com/tutorials/photoshop/line_tool.html ...and so on. Such was not the case for GIMP. In GIMP, you use the Shift key with other tools to draw lines. Not an inherently bad way of doing things, I guess. But here's how you have to find out about it:
http://www.gimp.org/tutorials/Straight_Line/ (That's from the official GIMP site, mind you.)
Hey, GIMP guys. Screw you and your sarcastic screenshot telling me what the "Shift" button is. Your interface is the WEIRD one. People who use MS Paint or Photoshop or friggin' ClarisWorks - your potential customers - expect "line" to be a tool, not a key. And it's not like the key is entitled "Shift Or Draw Straight Lines In Some Linux Programs." It is NON-OBVIOUS that this would be the manner you draw lines. I don't care that I had to look up how to use a new interface, but don't act like I'm supposed to psychically fucking know ahead of time how your arbitrary interface works.
Note how both MS Paint and Photoshop are way MORE straightforward in this operation, and yet avoid sarcasm in their tutorials.