1. You can certainly get laptops with XP Pro still. You may have to request no OS (if they give a discount) and purchase XP Pro separately. I wouldn't recommend mixing and matching. Probably won't hurt the network, but it does confuse things especially given some legacy software doesn't work with Vista. Most do. AC does.
2. The best person to ask (not that others don't use Vista -- but I know that of the people who do post here a lot, Adam does) would be Adam. He runs Vista on all his PCs, laptop and workstations. He is very happy with them. PM him.
