Exporting them as 8 bit PNG files with Alpha transparency would make a huge difference in file size, in almost all cases. You'll have to experiment with it a bit to see if the difference in the quality of the images will work for you.
Thanks. We did end up using Fireworks to create a large sprite of all the Home page background elements (some will be used elsewhere). We were able to get a roughly 1800px square file with the equivalent of what would have been 34 individual grahpics saved as one 100kb image sprite! Considering all elements had partial opacity, and a lot had soft glows and/or drop-shadows, that's a HUGE savings!
UNFORTUNATELY, Fireworks CS4 slowed to an absolute crawl on my ol' G5 Dual 2Ghz Mac Pro (with 6GB RAM). Even just selecting and element would cause a few seconds of spinning beachball. So I had to 'borrow' my bosses newer MacBook Pros to get anything done (not ideal!). And even with that, I had to install a demo of Fireworks CS5 for it to really work without a lot of delays.
And the Illustrator CS4 file DID NOT come in very nicely either. I pretty much had to rebuild most of it from scratch. According to the Adobe documentation, most everything I was doing 'should' have come in fine (I wasn't really doing anything that was listed as not compatible). Nice in theory...
It's too bad Fireworks seems to be Adobes ugly stepchild that doesn't get much attention. If they fixed performance and import issues, added a useful color/swatches implementation (from Illustrator/InDesign), and added at least simple paragraph/character styles (again - Illustrator/InDesign), we would definitely love to use this for website comps and graphics creation instead of Illustrator. But for now, unless we absolutely need Fireworks' 8-bit PNGs w/ alpha-transparency, we'll stick with Illustrator. It's too bad, I'm originally a Macromedia guy and was using Fireworks back in v.2/3.
When you importing Illustrator CS4 file, what kind of element you are having issue to import?
Regarding performance,majority of CS5 products drop suppot G5.
Do you see particular area of performance issue on you Boss's MacBookPro?