When opening a file which, for instance, requires notification of conversion from 16-bit to 8-bit, the notice dialog, which requires a response, is buried. So is the dialog which asks which of the file layers (the tiff and/or jpg thumbnail) the user wants to open. And the dialog regarding the conversion of the color space. All of this forced me to click on the "exec" window in the Dock to reach it and continue the file opening operation. (Alternately, I could move windows aside, hunting for the top level dialog, but that's not very convenient. Nor is it expected behavior.)

Other dialogs, such as the unsharp mask, also open up UNDER the main window. And there's no "exec" in the Dock to click on. One just has to push windows aside to find it.

In general, windowing in GIMP on OS X has a few problems. Windows are treated as separate instances, which is not how OS X is supposed to work. I should be able to Command-~ to rotate through all open windows related to a specific application. More critical, the window with focus is not coming to the top of the stack ... at least not on my computer. Someone who didn't understand what was going on would be dead in the water.

Mac mini, late 2009, OS X 10.6.8 (Snow Leopard)

It will be great when the interface issues are fixed, because the image tools are really great. I'm looking forward to making GIMP my primary image editor (in anticipation of moving permanently to Linux).