Well they are both out for a few days now. And they are pretty good.

Dreamweaver:
There is more change in V4 from V3 than V3 from V2 for dreamweaver. A few new things and a bit of interface changes.

The interface change is good, added a preview button, 'builtin raw html editor' ie. it can switch from html code to page design or half-half without opening a new window.

They added good referenece libraries, HTML, CSS and Javascript

Ability to debug javascripts (haven't try this out yet). But it seems like fun with breakpoints.

Added a Assest panel. to keep track of elements (images, colours, links, objects et...) on the site.

Click and drag table/table cell insertions. I still prefer to do the tables myself.

Template areas have more visual tags. ie. eaiser to identify which editable region you doing.

Editable flash within dreamweaver. Hmm, too simple flash modifications.

BAD things:
Uses more memory and CPU resource. Hmm, time to upgrade.


Fireworks:

Extensive GUI changes. Looks more like Flash 5 (may be good, but takes way too much memory and cpu)

It is starting to have more and more photoshop like features. They added layer masking. Collapseable layers (like Photoshop 6).

Better Marquee, allows save and restore (more like photoshop but nowhere as good)

Allow modification of rounded sqaure corners after drawing (about time).

Redone the colour pallates, now it makes more sense.

And a few other things.

BIG NEGATIVE: Very very CPU and Memory intensive program.
Making every object a sub-layer has its plus, but more annoying than useful. Especially when you are working with a couple hundred of objects.

So it is worth the upgrade? Dreaweaver=YES, fireworks=NO, a disappointment.