Test is here:http://www.anandtech.com/mobile/showdoc.aspx?i=2625
They had to buy them. The manufacturers make so little on these bottom end models they were reluctant to promote them by supplying review units.
They tested 3 Compaqs, including near identical models with Celeron M and Sempron, and a Dell and a Gateway. Alas no Acer.
Perhaps the most surprising result was the lack of any advantage in battery life for the Sempron with PowerNow against the Celeron M which lacks Speedstepping. It could be partly lower overall cpu power consumption and partly lower power consumption from the chipset. Which is why I'd like to see an Acer tested and see how much worse the SiS chipset is than the Intel. Acer's bottom end models use SiS chipset for both Cel M and Sempron. But they all seem to include wireless, unlike the Dell and Gateway tested.
Overall it's a very thorough test, as usual from Anandtech.
And that's five notebooks, but it will be six when Anandtech does a promised followup with the newly released low end model from Dell.