Paul, if you go purely on price/performance, then your chart says that Sempron will always be the best value. Of course, most people would much rather go for a dual core these days, and in this case, the point is the same. That is, on your graph, the Pentium D 950 is now only about 10% away from the price/performance point on AMD's most value oriented dual core while offering better performance in many critical apps (and by the way, the 920 beats it in price/performance). If you look at the rest of the lineup, however, it's not all that pretty. Sure, you may get marginally more performance out of the 4400+, but at a 25% worse price/performance, while the 4800+ may offer slightly more performance, at a cost of 60% worse price/performance.
The reality is that AMD is making a game out of dual core parts right now, with the vast majority of them being 3800+, and only a few being from the remaining 4 skus (plus FX edition). It makes it appear that they are way ahead in performance, but the only thing the mainstream can afford is their lowest end part. And compared to this, Pentium D is pretty reasonable, and priced so that it can ramp to the millions of parts.
You are going to see one of two things happen over the next few months. Either AMD is going to *drastically* reduce the prices of their dual core parts, or you are going to see a stalling of high end parts while AMD floods the market with low end Semprons and single core Athlons. They will try their best to maintain market share, but their high priced stuff is no longer desirable, now that you can get basically the same from Intel at a much lower price.
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