Legitimate copies of Photoshop are generally priced around $500(or more ? don't now really)
GimpShop - Free
Gimp - Free
Paint.Net - Free
Artweaver - Free
Paint.Net = the beginner-intermediate transition for a user
Artweaver = almost the same as above only a little more advanced
Gimp,GimpShop= advanced users
Photosop = Expert users.
This is my opinion, but GimpShop is for expert users too I guess. And it's totally free.
Free.$500 ?
What do I choose ?
You guessed it, I use photoshop too !
But really I love to test and work with open-source programs or free programs. It's so much fun for me !