I just installed WP 2.0 and I'm trying to import my old blog via RSS. I've been running into an annoying problem, though. After 10 entries or so, the importer gives up. Then, when I try to resume importing from the same file, I have to manually edit the post IDs and properly set the post autoincrement counter in the database. You might wonder why the IDs are screwed up. Well, it's because at every import the counter apparently increments before adding posts to the database. Example: You import posts 1-10 before the importer hangs, and they get the right IDs. Then, you import posts 11-20, but they get IDs 12-21.
The reason why I care so much about the IDs being right is that I want to continue using Haloscan for comments and the IDs can't change if I want old comments to be associated with the right posts. If I didn't care about IDs, I'd just keep importing until all the posts got in, regardless of what ID they got.