When I upgraded from UBB.Classic to UBB.Threads the #1 user issue I had was forgotten passwords. I understand that a lot of people are not tecno-savvy - a good number of them did not bother clicking on the "Log in" link or e-mailing me for assistance. They simply tried to re-register. And that's annoying!
Since then I have manually added a link to the "Have you forgotten your login information? Click here." page at the top of the Registration page ("Board Rules"). I highly recommend adding this link before you open your upgraded board. I also recommend that it be included in future versions (it should be simple enough to add).
Thanks for an excellent product!