http://cp.literature.agilent.com/lit...989-3122EN.pdf
I think this is the sensor used, the Agilent ADNS-6010. Previously it was targeted to high-end gaming mice; the thing that gives me this feeling is the four selectable DPI settings (400, 800, 1600 and 2000 cpi) in the hardware match the ones on the new Dell mouse very well.