Windows 7 is definately faster that Vista, I've been using it for a few months now and it hasn't been slow at all
as for pricing, it is currently $49 to preorder the home version and $99 to preorder the professional version, both upgrades, not full. that will go up halfway through august, then it will go up again another once or twice before it's actually released in october.
Personally, I've pre-ordered it already so I don't have to spend loads on it later!