I found it froze a few times, but if it had definitely stopped (by looking at the journal page on WP), I just hit refresh on the import page, and it got everything.

It didn't finish until after I'd hit post and got these comments though, so there are a bunch of comments on my queue that are assigned to teh wrong post, not that that really matters. It's nice to know I now have a backup of my whole journal on three different servers in an industry standard format though, just in case.