Actually, I used vbulletin's import script. At the time I did (a month or two ago) I had to rewrite a couple of sections of the script (the sql selects) as it was looking for the data in the wrong areas. Otherwise it just errored out. May be fixed by now, I don't know.
Unfortunately I already got rid of the modified version.
It does lose all postcounts and views. You can get the postcounts back by rebuilding the indexes and such - it's a 1 click operation once the posts are in the new db.