The Core i series has been a breakthrough for Intel. While since the original C2D there have been incremental upgrades this was a true breakthrough.
To put it in perspective the cheapest MBA at $999 will outbench ANY PPC Mac ever made, every Macbook (regular) ever made, every Macbook Pro prior to 2010, every Mac mini prior to the recent model, every iMac as recent as late as 2009 (only the highest end 2009 27" beats it out too), and most shockingly the original Mac Pro in any configuration, including the Quad 3.00ghz Xeon that was king until 2008.
That also means the $600 Mac Mini will outbench all of those computers as well.
Of course this just tests CPU.. no graphical performance, no hard drive performance.. etc.
Still, it's pretty amazing to think. I remember a post just 3-4 years ago asking if the original Mac Pro would still be a beast in 10 years.. although I knew technology would catch up to it. I didn't think in less than half that time we'd have our lowest end computers outbenching it.