I recently updated to GIMP version 3.0.0, and the first thing I noticed is: it takes 3x as long to boot up.
Discussion
Hm, I hadn't noticed that. My ancient i5 laptop still running it a-ok.
Did you compare it with GIMP 2 though?
I use Gimp on an almost daily basis, and have been using the beta for months, side by side with the old to see where they have improved. I didn't see a major difference on old or new hardware.
