I've never had ANY of those problems with GIMP, so I suspect the answer to your question is simply that people who like it haven't encountered the issues you have with it. I don't have PS, and I have a mac, so I use GIMP and it works pretty well, given it's freeware. I would say that PS is obviously a better option if you have it, though.
What OS do you have, Muse, and how old is your computer? All that stuff really sounds like corruption somewhere, either in the gimp drivers themselves or in the computer software permissions. It shouldn't be doing that stuff at all!