Well, if you have access to Photoshop, you might as well use it. If you don't want to spend any money, use GIMP.
Ther GIMP does everything I need, it is as powerful as PS, it is easy to use, it is free, and it works on Linux. No contest! I have better things to spend $1000+ on ($AUD).
I voted that both are great. I think the difference in price point make these two really hard to compare direclty. Photoshop is an excellent, high quality/high priced piece of softare. That's great if you're a graphic designer and can get full use out of everything it has to offer (and can afford the price tag!). IMO, most of the people who are using photoshop don't need or use most of the features that differentiate it from alternatives like the Gimp. I've just started using the Gimp but from what I can see it has a pretty good set of features. For the price, I think this is a perfectly suitable alternative for most web designers. I also like that it's a lot less resource intensive than PS - a much better choice for simple tasks. So, quite different applications really - one for power users, one that's more suitable over the average user. When you take the price tag out of the equation of course Photoshop is a better product - but when you consider how much you're paying for it the Gimp looks much more attractive. I agree!
I don't have a graphics tablet, but using Wacom Graphire as an example, according to a cusomer review in this amazon page, The Gimp does support pressure sensitivity. You can also find other statements around the web that it does not, but maybe it's an issue of getting the correct drivers installed. If you want to simply believe The Gimp docs... http://docs.gimp.org/en/ch07s03.html
Photoshop is awesome..but for $0, Gimp is pretty damn good also. I think the average person is well served by Gimp, but if I had to hire a webmaster who used only Gimp, I would pass. Photoshop has too much functionality that a pro needs.
i do indeed dig my photoshop. I tried the gimp when i was testing ubuntu because i <3 the antialiasing everything. if anyone knows how to force this one windows i would love you.