I have GIMP and have played with it on and off. I don't find it particularly easy to use in some respects.

As for Adobe products, I resisted the monthly fee "rental" system for years, having found a free, completely legal, downloadable copy of CS2 on the internet. However, I've had to upgrade my laptop as, being 10 years old, modern versions of some software won't work with the software on my new cameras. As I'm getting more and more paid work for photography, now I don't begrudge keeping up to date with Adobe and use Lightroom and Photoshop almost every day.

For a quick'n dirty layer draw program, I use Pixelmator - very cheap when I first got it.