On one site, I actually have a section of my WWF forums (with dynamically generated URLs and all) rank HIGHER for a set of keywords I would prefer another page on my site would rank high on. And the other page has keywords in the URL, and the forum section does not!

Both pages are on the same website and are major pages, both with lots of links in, but the forum page ranks well for one set of keywords, and the other page ranks well for another (both are in top 10 positions in the rankings, by the way).
I think the search engines are starting to downplay the importance of keywords in the URL because too many people have caught on and have started to use that technique to spam the index.
The search engines want people to focus on good content, and will keep adjusting their pagerank or site scoring to reflect that goal.
Long term strategy should always be content, content, content... and good content at that.

Oh, and RSS feeds of your content seem to help more in my experience than what's in the URL.
There is one case where a dynamic URL will not be indexed by Google (and perhaps others). If the URL has "id=" as one of the parameters, then the page won't get indexed. Other than that, dynamic pages get indexed and rank well.
Edited by wistex - 02 April 2007 at 8:43pm