Based on the
Wikipedia article, my take is that hyperthreading is a "poor-man's" multicore whereby certain parts of the core are duplicated, but not others.
It should be pointed-out that Intel currently sells a
quad core processor (although it may be two dual core processors in one package) and AMD has a quad core processor coming out in August. AMD claims that their architecture is better because it resolves some alleged memory bottleneck in the Intel design.
Disclaimer: I'm employed by AMD, but not in the processor department. To be honest, I haven't been following the recent evolution of processors carefully.
If I was purchasing a new machine, I'd get nothing less than a dual core 64 bit processor. It might be overkill for today, but new software has a way of eating-up every available CPU cycle.