The GIMP is like Photoshop 4 or 5. One of the worst "open source alternative" to proprietary software. It's an antique piece of software that hasn't caught up with the last DECADE of innovation.
If PS is so much better, why don't you use it? What non-destructive tools are you talking about? I don't think tools are typically destructive in Gimp?
But you are correct, I am not a designer, I am a developer.
A Smart Filter will be reapplied to the object every time you make changes to the object. But not in an "applied twice" way, because changes are not set in stone, it doesn't degrade the original object.
Photoshop is so much more productive than the GIMP. Anyone who pretends that those two packages are equal should keep from talking about image editors.
Anyway, I am definitely not a power user - I think those already know if they are going to use Gimp or PS, and will not be swayed by HN discussions. I am just tired of the interface argument, because PS is definitely not easy to use. You have to dig through some tutorials and then you suddenly know how to do things, but it is not intuitive.
If you need specific PS functionality, obviously you have to use PS. My point was merely that the user interface is not really the big differentiator. (Also, I don't know the latest PS versions so I might be wrong, but I doubt it).
One problem for more advanced work could be that there are more tutorials for PS than for Gimp.
(I only use Gimp because I don't want to pay for PS and I tend to be on Linux at times).