I don't use Photoshop, although I have loads of different versions going way back and up to CS4. None of them are installed on my PC for the simple reason I'm not it's biggest fan in any of it's versions. In pretty much any of it's forms it's a huge drain on system resources and can be irritatingly slow even on a fast machine.I also find the working area restrictive. If you come by CS4 etc honestly then it's also.hugely expensive. Is it worth the money? Of course it is - it's an absolutely immense programme, but for photographic processing it's questionable if you'll ever use more than 10% of it's potential to be able to do anything at all in processing your images, and for that reason I'd never advise a newbie to spend hard earned cash on Photoshop which could be spent on much needed equipment - there are plenty of alternatives which wont leave you feeling short changed.
The problem is though that Photoshop was in there early in the market place and we now say an image as been 'Photoshopped' when it could have been done with any number of alternative packages- the name 'Photoshop' has become synonymous with digital editing to the extent that many people just dismiss the idea that there are any viable alternatives out there.
What I will say is that if your needs go beyond normal photography to the extent that you produce some of those fantastic images we see which are a blend of conventional photography and graphics, then you'll perhaps start to see some of what you paid your money for with Photoshop. If you're an out and out graphics designer then Photoshop is probably for you - it does have some great filters and effects which you're unlikely to use seriously otherwise.
I have to say there are some problems with going elsewhere, especially in the early stages when you may need help. Go on any photo forum and shout for help with Photoshop and you'll be deluged with the responses - such is the strength of it's popularity, and there are far more independent plugin applications available for Photoshop than any of the alternatives. Whether you actually need many of them is another matter, and the better ones tend to be available for Photoshop and Paint Shop Pro.