Web design is not just about Photoshop. Though i will disagree with some of the posts here. Photoshop and ImageReady is a good combo for designing websites. Though Fireworks makes some items easier to work with (e.g. rollovers, animated gif's), ImageReady can do just the same. I thank Adobe for finally speeding up IR in the PS7 bundle.
To continue. Web Design is just as much about Optimization, User-friendliness/Accessibility and Color psychology as it is about "design". A lot of people laugh at me when i say this but other professional designers would agree with me (if not to an extent)... Web Design is a science of the interaction between media and people. Not just about "sitting in front of the computer tinkering with Photoshop filters."
However, it is by tinkering with Photoshop that you learn best how to use its features.
Learn the theories behind different kinds of media and how the Web differs from the traditional. That's one step towards being a good Web designer. It definitely is a fun process if it really is your calling, but you do have to put a little grunt every now and then to actually be good at it.
A word of advice, don't narrow your skills to just plain web design. In this day and age it helps for you to be multi-disciplinary in your approach. Learn beyond what you think you need. Scripting (CF, PHP, CGI/Perl, etc) and the theories of programming will go a long way in helping you become a well-rounded developer.