It is very elegant design and ux makes it really easy to understand and work with gimp. Works best on mac and windows and Linux too. Also it is best fast and light weight tool for photo editing. The learning curve for editing is seamless. It is handy in designing the sprites and layer by layer selection

open source and vast amount of tutorial as well as addons

Gimp has countless options to create all types of designs, its interface is very similar to other software, what I like is that it is very light and has the possibility of downloading add-ons.