Yep, we are definitely doing things right over here!
As said we launched our new website on Tuesday and implemented Google Sitemaps in it. We have registered the sitemap and Tuesday morning around 6 o'clock our time the sitemap was downloaded by Google.
Now on Thursday some two days later we see already many pages in the Google Index. When I do a search on the first 100 pages changed in the last three months on Google I find that of these only 12 are still pointing to our old site. My guess is that these are there only because we had some problems setting the rewrite rules for the old asp files.