On the 8th March I 301'd four folders containing 3500 htm files to a new URL. The toolbar PR has transferred to the homepage and menus but not yet for the individual htm files, almost all of which are supplemental. As expected traffic is lower but had already been falling since the Big Daddy update.
I don't quite understand how this works either. I can see it's a good way to help search engines know the old page is gone and that they find the new location of the page. But I can't see how any inbound links to the old page could help the new page. I hope someone here knows the answer.
in my past experience when setting up a 301 of an old domain with PR and backlink to a different domain it takes quite awhile for the link and pr equity to transfer over. it eventually does but i have seen it take over 6 months for everything to move over (front page, all internal pages)
In early 2007 I changed my urls to SEO url format (i.e. product-name.html) and 301'd previous url to new SEO url format. Toolbar was grey for two months then over the period of two weeks PR began to reappear. My new SEO urls were completely indexed within 2-3 months. Then about 1/3 went supplemental. The SEO urls were implemented to regain previous high rankings. Seems I've gone from -950 to -30, so it's better but still not as good as pre-August 2006.