Hmm, that’s odd. I migrated my web design site https://webjones.org from TextPattern last weekend using the import-textpattern.php file that shipped with WP 1.5.2 (whatever the version was right before this last big upgrade). And I had been using TextPattern 1.0rc1. The only problem I had was in my new WP install, I had forgotten to set up my categories, so they all got dumped into “General,” but this was good because it forced me to clean up a bit. All the posts and comments came over just fine, but I noticed that the dates were off quite a bit. But since I was cleaning house anyway, I just fixed each one of those as I went.
I wouldn’t mind knowing why the dates were off kilter in the import, tho.