AMD HyperTransports
While AMD and Intel have gone back and forth in terms of CPU speeds and performance, I've preferred AMD's HyperTransport with the dedicated memory controller on the CPU itself, rather than requiring the NorthBridge to deal with all main memory access. Now that Intel is switching over to the same type of design, one of the main advantages of AMD's architecture is now moot.
I don't really care about Intel's Hyperthreading support, as a 4-core CPU running 1 thread apiece is still going to potentially quite busy in terms of memory access and so forth, and relatively few apps out there are going to show a difference between 4 and 8 threads. On the other hand, the ability to bump up the clockspeeds by a notch or two when the system is mostly running a single thread strikes me as a nifty idea.