Well, last night's ephipany was right-on.  I finished DasBlogRadioCommentImport and ran it last night, importing hundreds of reader comments and successfully integrating them into each related dasBlog entry.  Let me know if you want the code via email.  When I get access, I'll post it on the GotDotNet workspace.

All in all, the Radio "conversion" was a big stick of butter. Here's the goodness:

• Taking Clemen's lead, I modified my Radio template to include JavaScript and META refresh tags.  Some Details here.
• dasBlog handles these redirects with a regular expression based $g(Url Rewriting) Module that is pure genius.  I added a series of expressions that didn't exist in order to handle Radio Categories and Radio Stories.
• I imported all the Radio content with the included DasBlogRadioImporter.  Good.
• Then I wrote DasBlogRadioCommentImport.  Better.

All in all, for existing Radio Userland users, dasBlog offers a fantastic migration story.  All my existing Google Radio links work.