It's not clear what Apple will do with this purchase. Right now in 2008, this 14 Watt 2 GHz dual-core chip seems inappropriate for most of their current products, although it's possible a derivative could be used in products like AppleTV (and theoretically a low power laptop), or other products that have not yet been announced. The benchmarks of this chip are listed below:
At 2 GHz, each core achieves a SPECint2000 score of 1,000 and a SPECfp2000 score of 1,500. Running SPEC benchmarks, each core dissipates around 7 W max; a SPECint/W of 142.8, about four times more power efficient than a Core 2 Duo processor.
Those speeds roughly are equivalent to about a 2.8 GHz Pentium 4 and a 3.4 GHz Pentium 4 Extreme for SPECint2000 and SPECfp2000 respectively, for each core of the PA6T-1682M.
Forbes postulates that Apple intends to use in-house chips for the iPhone (and iPod) platform, and I would agree that is a strong possibility, especially since the acquisition was led by Tony Fadell, Senior Vice President of the iPod Division. It would take a new chip design for this purpose, but it's plausible that P.A. Semi already has some such low power designs in progress, also based off the PowerPC architecture. It's of note that the founder of P.A. Semi had his roots in the design of very low power StrongARM microprocessors. Another notable piece of trivia is Apple helped develop the ARM architecture and put an ARM chip in the Apple Newton.
This news comes the day of the Apple earnings call, which will occur after the market closes. So far AAPL is up to $163 in pre-market trading this morning, up from a close yesterday of $160.20.
[Update 2008-04-23]
EETimes says Apple doesn't actually care much about P.A. Semi's chips.
P.A. Semi customers were told the acquiring company was not interested in the startup's products or road map, but is buying the company for its intellectual property and engineering talent.