When you can get something that good for $60 there is absolutely no reason whatsoever as to why you'd put up with something like The GIMP. None. Photoshop had things like Adjustments Layers since 1996 with Photoshop 4.0, the same version that introduced an easy method to make your own automation (macro recording). 1996. The GIMP can't beat something that was made in 1996. I'd rather put up with a VERY old version of photoshop running under a PC emulator with an old OS than use the GIMP. That's how different the two software package are, and how useless The GIMP is.
I have tried to convince myself to put out some photoshop plugins, but I just don't see many people buying the plugins already out there.
Also the photoshop plugin API is crufty as hell.
What percentage of plugins out there are being rewarded well by the marketplace? I would bet that there are only a few plugins on the market right now that make a noticeable amount of profit.
http://registry.gimp.org/taxonomy/term/366
"This plug-in enables you to use the vast number of existing filters made for Photoshop's Filter Factory"