It's pretty much the same product as imageready. It's easier because it has less functions than photoshop. But yeah, lots of people use fireworks. It's much more web function than imageready. You can do some pretty nice dhtml pull down menus in there, as well as some advanced rollover and swap image functions.
The bigger question might be how long it will be around. Since Adobe and Macromedia have merged, one can only wonder which overlapping apps will disappear. I'd guess Fireworks will be lost, but some of the functions will be ported to PS/Imageready. On the other hand, Dreamweaver will remain and GoLive will go away. I can't think of anything from GoLive to port to DW. :)
I use and love them both (Studio 8 and CS).
But, for fast web work. I find Fireworks is easier to work in and way faster and much more user friendly than Photoshop, Imageready and Illustrator.
When working on Art with brush work and detail, I would use Photoshop.
I would use Illustrator for vector as needed, not much for the web.
I would just use Flash for most "if vector" is needed for site work.
But If I'm working in DW. 99% of the time Fireworks is best.
For me Fireworks and in Studio 8 apps it's that "Properties Panel" that helps the most, no question.
Quick control. Plus with MX 2004 and /or Studio 8 everything is even better with workflow.
I hope Adobe doesn't kill Studio 8 as a web solution.
GoLive should just be dropped, Just as FreeHand should.
For most Web work, I think Fireworks does a great job.