I think as long as it's displaying some of the special characters correctly then it's probably ok. The big thing would be to check a post that is showing improperly in the db, and looking at it in the script to see if it's displaying those characters properly. If it is, and you can edit the post as well, without any issues, then you're probably safe.
You could possibly try changing the charset that MySQL uses before the import is done, as I believe it uses latin1 as the default, but if old posts are displaying properly and new posts are ok, then you might not need to go that route.
