It depends what you're using it for dude.
For pretty much everything. I plan to use TTH to learn Photoshop and then try to create as much as I can with it, but that's if I do end up getting it.Gimp is similar, but nothing can truly replace PS, imo. It depends what you're using it for dude.
Here is your Right Answer.For 90% of Photos Work, any decent program will do just fine. However, for Professional Graphic Designer, Photographer...et, Photoshop has no Competition
Exactly... I messed around with Gimp for a year or so just for making my own banners for CB products or cpa offers that don't provide them in affiliate dashboard. It did the job for what I needed but then I got a free trial for PS and there was quite a difference in the quality.
I suggest you give gimp a try for a few weeks to learn your way around the tools and their capabilities and then get a trial of photoshop and make your decision from there.
As was said... it really depends on what you are trying to do when deciding if it is worth it. I did not continue with PS cause Gimp did a good enough job for my limited needs.