I'm sure it will be virtually undetectable.
As for when... anytime now, probably.
Everything has been copied across, the redirects are being implemented and hopefully the DNS propagation shouldn't take too long - but that is always a bit unpredictable.
To be untypically serious for a moment, I know a bit about the day-to-day running of a forum but, frankly, very little about vB and HTML coding, server maintenance and all the other things that make Pixalo possible, so if I happened to be wearing a hat I would take it off to Steve and Dave for knowing the right incantations to intone.
Without them, we would not be here.