I've just completed the migration of my blog from the old (really old) Movable Type version I was using to dasBlog 1.8. It was actually a lot less painful than I expected, but I was able to take advantage of MT's very powerful templates to pretty much generate all the new dasBlog datafiles needed.
All content in the old blog has been imported into dasBlog and I've set up a redirection mechanism so that if you browse to an individual archive page (say /weblog/archives/0000XXX.html), a 301 permanent redirection will be returned to the entry in dasBlog. Also, the main RSS feed has also been redirected to the dasBlog-produced one, which is hopefully working fine :)
I've also created a customized dasBlog theme for my blog which is somewhat similar to the one I was using with MT, but somewhat nicer, so for those of you browsing to the actual page it should look fine (any suggestions/criticisms are welcome :))
Finally, you can now access the individual category pages (which dasBlog of course generates automatically). I created and categorized my blog entries in MT months ago, but had not made them public, but now they are, so feel free to subscribe to specific topics.