The first impression is positive (using Win10 version). It's faster than before and seems to use only small amount of cpu resources which is really great feature for a paint program. In comparison when you run something like that awful Windows 3D Paint it's way much demanding for the processor. Gimp is quite large software with 8000+ files so it's surprising how snappy and fast it feels.
It's designed mainly for image manipulation, but I think it's missing an opportunity to be more than that. I would not use it for serious art design only for the reason it has a context menu in right mouse button. And you can't configure it to anything else. For painting it would make much more sense to have a secondary color, eraser or something like that in the right button.
It also could have a "tiled" grid to show tile areas (when drawing tile graphics) with regular grid you could configure to pixel size. It does have a small preview for image, but that preview could be configured to show a small area in repeated mode to preview tile seams. Those are perfectly possible features to have, but I just know they will never do it. Another obvious but missing feature is any kind of shapes including a line (which is hidden in form of shift+pen).
Strangely Gimp does have a new brush engine which is quite nice so it's weird that they support painting that way. Also, another strange thing is that you can't put color editing on tabs, but there is a palette for selecting colors. When you need a new color you have to edit it on a pop-up window each color at a time. All this makes the software feel like it doesn't know what to do. Is it only a image editor or is it also a paint program?