We have a new Sun T5220 with the new Niagara-II chip in it. I don't know if it's 8-core/8-thread or 4-core/16-thread but it shows up in Solaris as 16 CPUs.
I'm running a cpu-intensive process (bzip) and prstat is only showing it as using 1.2% of the CPU. On another older system, the same bzip takes up 25% of the 4-proc box.
On the old system, it's clear that bzip is a single-CPU bottleneck (because it's single-threaded). On the new one, well running full-out but only taking 1% doesn't look like much.