I will tell you from personal experience that photoshop is not an easy program to learn, especially if you don't have a deep interest in computers. There's just so much to it, and if you don't use it on a daily basis, so much to forget. Go and look at a Photoshop training book, and then understand that this 500 or 600-page book just outlines what's *in* the program, and that mastering any of it takes a lot of time. Photoshop IMHO is for those digital-age people who, 20 years ago, would have had an equivalent in a professional printer -- somebody who might not enjoy the actual photogaphy as much as the darkroom work.
If you're mostly a photographer, the stuff you have, plus Lightroom, would probably do everything you need.
If you find that you have an interest in compositing, then you'll need PS; if you have an interest in special effects, or if you're an architectural photographer, you'll probably need it. And if you like computers, and messing around with images, there are aspects of PS that are simply fun to play with -- You can make 60s-style acid-rock posters for your kids.
For myself, I finally have decided that life is too short. I have PS2, and probably won't upgrade for a few years, because I only use about 1/1000 of the program that I have. I plan to shift my main effort to Lightroom.
JC