Well, there is no one-size-fits-all answer to this. PS aficionados may look down their noses at GIMP, but that's not because PS is 'better' than GIMP, it's because they think they're better because they use PS.
I don't like Gimp primarily because I don't like the way it's configured, but you can't beat the price, and it has a fair amount of features. I agree with much of Unpopular's post regarding GIMP. That said, it's pretty amazing for free.
I use PS CS4. To answer (I think) someone's question about whether PS is easy to use...I didn't find out that way. I didn't find it to be intuitive. I've learned slowly, and have gotten used to it. It's very very powerful, but I would never describe it as intuitive. Or cheap. Thankfully I get educator discounts (
one of the few perks of being a teacher), which takes the sting out of it. I'm glad Nik Software makes plugins for it. I started using this a year or two ago, and fortunately find Nik to be intuitive and effective. Whew!!! Anybody who has ever found PS to be intuitive, what can I say, you brain is wired differently than mine, and my hat's off to you!!
If I had to use another software besides Photoshop, I'd probably use either Elements or Lightroom maybe.
Oh, and I don't think I'm better that I use something over something else. I doubt very many people do. We all know that one of us might be struggling along with Photoshop CS5, and there will be someone else who has no money running a twelve year old computer held together by rubber bands and Elmer's Glue, and they're using whatever horrible program that came with Windows 98, getting better results than the rest of us, so I never cop an attitude with equipment (or for any other reason, for that matter).
BTW, there's people taking better photos with iPhones than some people running around with Hasseblads. Sure, I'd rather have a Hasselblad, but the fact remains that some people are getting phenomenal shots with iPhones.
Thanks for listening.