Once downloaded and launched, the betas will only be active for 48 hours -- unless you have a CS3 license. Creative Suite 3 customers will be able to extend the trial period (presumably until the final versions are released, though the deactivation date is not mentioned in the press release).
The Dreamweaver beta includes a much-anticipated (at least by me) change to the WebKit rendering engine for previewing and live editing.
Fireworks has been re-vamped to look and feel more like other Creative Suite apps, and now allows users to export design comps as interactive PDF documents.
The Soundbooth beta now includes multiple track support, and the new ability to match volume levels across multiple files. Plus, users can preview MP3 compression settings before saving them.
Soundbooth (719MB) requires Mac OS X 10.4.11 or later, running on an Intel processor. Fireworks (634MB) and Dreamweaver (262MB) have the same OS requirement, but can run on a G5 processor or better.