I've noticed a couple of things after the process.
1. Forum permissions did not carry through properly as far as usergroup access is concerned. In other words, the specialized forums where only certain usergroups should have access didn't retain those permissions.
2. Thread prefixes are not showing as being copied over. Haven't checked the DB yet (I'm still rebuilding the search cache). But none of the defined prefixes from IPB are showing in the ACP for XF.
Still going through things with a fine tooth comb. Looks like all the posts and users carried over, but even with the permission test button, it's a bit of a pain to go through and test each forum to ensure the proper viewing and posting rights are correct.