Not really a multiprocessor laptop (though I have heard of such a beast). The hyperthreaded CPU (intel P4 HT) has some tricks it can do with the way it schedules operations so that it can act (almost) as if it was actually 2 cpus. If you really want to know how it works, there's a good writeup on ars at http://arstechnica.com/articles/paed...rthreading.ars
The point is, if you have such a processor, and compile the kernel with SMP, you get a /proc/cpuinfo that reports two cpus and programs/libraries that can take advantage of it actually do see a speed improvement. I play around a lot with raytracing as a hobby and get impatient at times, so the "second" processor is nice (can render two frames at once with only about a 10-15% performance hit on each). But I also schlep the thing around alot, so the suspend functionality would be just as nice most of the time.
I believe there are other cpu's besides the intel p4 that can do this sort of thing. I'd be surprised if amd didn't have something just as nice, but I don't know for sure.