Photoshop does tend to be the "de facto" standard (whatever de facto) means
- I however love fireworks (macromedia), find it much easier to use than photoshop, I have both but I use fireworks 99% of the time. Imageready is great for the effects/filters you can apply to images.
- If you have the knowledge required to use it, photoshop in the end is probably the best/most powerful tool for any type of graphic work. An example of a photoshop user on this site is vStyler, he is a "master" status user on this site, he makes some of the best wb skins you will see on this or any other site and he is a photoshop power user, he "lives" in that environment so if you're looking for a correlation between application & type of user, that's as good an example as I can come up with.
I guess if you're just starting out, you have alot of reading to do.
Find out what's available, what your own skill level is, find out what you're comfortable using, etc.
As a beginner (nothing wrong with that, we all have to start somewhere),
Start with free tools first and take it from there. Once your skill level increases you'll determine whether or not you will benefit from paying for advanced tools like photoshop.
... just my 0.02 cents cdn