Me too.
Curiously, there seems to be some sort of a small anti-Photoshop movement regarding modding Openxom. I don't really understand why.
Well, I've tested with CS2. I open the test image I made earlier
1) Color zero becomes transparent in editor, and is actually turned transparent when you save. In the case of a sprite (not a flat background) you could consider it helpful, but I think OSX verskion of OpenXcom can't load GIFs correctly when they have transparent background.
2) I see absolutely no way to differentiate between colors 15 and 255. If I use eyedropper in the "255" area and then paint, the resulting pixels are in color 15. If I save the image's palette and use it as a color swatch, when I pick the last color and draw with it, it's color 15, not 255.