What's so good about The Gimp?

I've installed The Gimp onto my Mac for editing photos and doing cool stuff as I hear it's the open source Photoshop equivalent.

I just need to figure out how to use it! Can anyone tell me what useful features it has that I would want to use to edit photos, and if they know of any useful online tutorials?

I've gone through The Gimp's tutorials, but I've found them confusing. It tells you to do things, but doesn't give instructions on how to do it. It seems to assume you know where all the buttons are and how they work!

Maybe I just need to go through each tutorial thoroughly?? I guess my main question is - is it worth it??

I've got Nikon software called Picture Project that came with our camera that allows me to get rid of red eye, sharpen images, lighten dark spots in images etc. If anyone can tell me some useful features of the gimp, I'd love to hear about it!