Hello Jeff,
First off let me say how very happy I am that you're working on this, and that you've been allowed to make it accessible to us all. I know you're busy, so whenever you can get back to me is good.
Linus box over at DreamHost.
Using latest WP build with vB 3.6.8; I know that's not technically the supported vB version, but so far everything's worked smoothly. The only weirdness is the fact that the two users I had in WP, it's a new site to soon replace the current one our community uses, were overwritten/altered after I mapped the users from vB.
Both users were pretty much identical to the vB versions, even using the same emails, and I would have chalked it up to that, except one users actual username was changed into a user on the forum that has no relation to them.
Example: WP User#1, bobtern, was changed to username Bob Tern; that's not really an issue, as it's the same person. WP User#2, eddierock, was changed as well, but this time to username Francis Drake. Francis Drake is a username from vB, but it's not Eddie.
There's no other list of users in the WP user list, but I'm thinking they don't show up there from vB. Both existing users in WP can use the correct user/pass they have for vB to log in (Eddie uses his vB user/pass, not Francis'). It's just the username fields in WP for them show the vB usernames, with one being incorrect.
If you need any other info let me know, thank you.