Well, if an 800 Celly overclocked to 1.2 gig is equivalent to a 1 gig PentiumIII (even on a 100 FSB), that's a heck of a cheap way of getting the same performance, since a Celly costs maybe $50 ($85 if you get a guaranteed overclock one).
But I think it's too good to be true and I presume it will perform equal to an 800 PentiumIII, or even worse on some benchmarks. Although even 800 chips are running around $150 now.