Well, judging by the results I have gotten with the trial I would use it all the time. I take lots of pictures and end up editing and fixing a lot of them. I have been using MS Digital Image Pro and it works OK for a lot of stuff but I never thought I could get results as good as I have gotten with PhotoShop. Here's an example:
Before
After
It was a stupid mistake to take pictures through a tinted window which I did on a trip to Utah. I took quite a few that way and couldn't see the effect on the tiny camera screen. No matter what I did in Digital Image Pro I couldn't get it to look any better. After a few clicks in PhotoShop and some color balancing it came out like that.