I tended to use Corel Paint Shop Pro 13, but I also use Gimp and find it to be very good, although its not the most user friendly menu the first few times you use it. With the Mac I use Aperture 3 now.
I'd highly recommend you give Gimp a try - It'll do everything my fairly expensive paintshop pro/Aperture 3 will! Being free is a very big bonus too!