Aaron Brazell, the mastermind behind Technosailor, is, as they say, Good People. I pinged him the other night after banging my head against a wall trying to get my WordPress blog exported properly. The issue was my reliance on Textile when drafting posts (this started in Movable Type, and I continued doing it once I converted to WordPress. And the default export script in WordPress doesn't trigger any plugins when it exports the text, so my 2800+ posts were mostly useless for a Blogger import.
Aaron whipped up a plugin that did exactly what I needed, and I now have my entire WordPress archive in a usable export format. A "thank you" seems hardly sufficient, but I'll start there: Aaron, thank you. :)
Some other lessons learned: my first few attempts at exporting from WordPress failed and it took a few tries to learn what was up: the default timeout setting for PHP is 30 seconds. My WordPress install lives on a shared server, and exporting 2800 posts and 9000 comments was taking longer than 30 seconds. This page was what I needed: editing the export.php file (in wp-admin/includes/) and adding set_time_limit(120); to the script did the trick: that gave the script plenty of time to execute and ensure I got the entire blog exported.
The conversion will continue - next step is to import the posts into Blogger, then figure out the most efficient way of rewriting inbound links so that links to the old site (in the form http://www.rklau.com/tins/archives/yyyy/mm/dd/post_title.php) are rewritten to the new site (which will be in the form http://tins.rklau.com/yyyy/mm/post_title.html). That should be relatively straightforward.
In the meantime, FeedBurner subscribers should be seeing these posts now as I've updated the source feed to point to the Blogger-maintained feed.