You know, this is a really good question. I don't think it's a coincidence that apple just updated everything in their line (except the mini) with some sort of decent graphic card. It seems that the focus of snow leopard's optimization will be using graphic card power in everyday computing. Unfortunately, everyone with a MB and a MBA up until very recently won't see any benefit from their intel graphics. As far as 64 bits, again I could be wrong, but doesn't that help addressing larger amounts of ram, which won't help an MBA with it's unchangeable 2gb of ram (or even a maxed out MB with 4gb). There probably will be more improvements which apple hasn't made clear.