You're also going to want to check your NICs, especially those connecting to storage resources, for TOE. That stands for TCP Offload Engine, and it was introduced as a hardware-level acceleration feature by companies such as Intel well over a year ago. The idea behind TOE is that big TCP operations get off-loaded from the operating system (meaning the CPU) and run directly on the TOE card. This'll help for those high-performance TCP operations, but it'll especially come in handy for big chunks of iSCSIness, too, hence the storage stigma. I'm not saying you need to run out and upgrade anything that doesn't feature TOE, but it should certainly become part of the feature requirements the next time you're shopping for hardware.
Obviously, it's going to be a Long road to Horn, and I've only just set my furry little feet upon it. But if you're thinking that Longhorn and Vista were built on the same code base and you already know most of it — well, you're wrong. Network performance, remote access performance, management, loads of security features — the learning list is going to make your eyes pop around like Sauron's. Hell, Brian Chee and I still have to figure out what to do about IPv6, promote or pooh-pooh. It's going to be a long summer.