Forum Moderators: Robert Charlton & goodroi
If your specific situation makes that a heavy-duty job, then consider only using 301 redirects for the urls that have external backlinks or lots of search engine traffic. Googlebot will crawl the new site structure over time to discover the rest, and you can submit an xml sitemap to help things along.
There is often a short term hiccup in Google traffic when you make a major change like this. My advice is to deploy the new version in a test environment first, and really debug everything you can find before you go live - especially canonical url issues [webmasterworld.com]. I've yet to see a redevelopment like this with no problems on the intial set-up.