I like that it's free and open source. The UI is simple and easy to get used to. It has some very useful features in terms of image processing. There are some things I dislike about the program. One is that it does not have an option to save images as PDFs or JPGs.
The other thing is that it's not as stable as other programs such as Adobe Photoshop. It crashes every now and then. But, if you're looking for a free, easy to use, and open source program for compositing images together, then thisβ¦