I imported my old comments quite carefully, which included email addresses, so for those already with a disqus account you may find that if you do a profile merge you'll be able to add any comments you made on this blog to your disqus profile.
There are a few problems with formatting of old comments, but mainly they should look right.
There are redirections in for feeds, and permalinks should be identical but your feed software may get confused and mark posts as new - sorry for any inconvenience.
My motivation, for those interested:
I found I always wanted to edit posts in my editor on my computer, not a web browser. Copy-pasting from there got tedious.
My comment system was falling behind and becoming inconvenient for people.
Editing my own blog software became a pain. Written in Haskell, I had enormous pain with “cabal dependency hell” whenever I came back to it after a system upgrade (there are solutions, apparently, but I lost the will to learn how to use them).
It's just so much harder to go wrong or have performance problems with an essentially static site.
It's nice to have everything under source control.
Blogofile works nicely. I used version 0.7.1, which copies the 'controller' code into the current directory. This allowed me to add the few things that were missing (mainly my 'Related posts' feature) and make a few customisations.
Blogofile also now handles all the other static pages in the site — not a huge number, but worth having a decent templating solution for.
It also allowed me to try out the mako template engine which works very nicely. I also used it to convert the old comments to the WXR file that disqus can import. When you need the full power of Python in a template, mako is great.