Maybe you can find something useful from this digitalpoint's forum thread describing the results of moving from vB to xF. Seems like other than improvements there's no any negative impact (except being nagged by some vB fans forum members )I decided to move xenforo from vb 4.2 but there is a question I want to ask.
what will happen to google indexes? am I gonna lose all of them? I'm using vbseo. I know there is a url redirection scripts but it means all the threads going to reindex by google? am I right?