Photofiltre happens to have less features but is free for non-commercial use .

Personally, I use Paint.net. If you're used to GIMP then it might not be as big of an issue for you, but I found it extremely crowded and user-unfriendly.

Paint.net has all the features that I personally use, and has a very nice layout.

I'm using a XP-Pen Star G430 OSU Drawing Tablet  for my drawings in Paint.NET, and it works pretty well but does not support pressure sensitivity..