I got the Michelin Cyclocross Jets in 700x30 (which ends up being way wider once mounted...more like 34c or 35c). Coming from the stock Kenda Kwick's, I wanted smoother rolling resistance without sacrificing too much singletrack capability. It definitely feels easier to maintain speed on pavement, but haven't gotten out to the singletrack yet. Will let you know.

FWIW, these are generally considered too soft for pavement (wear out fast), and better suited for off-road use. Whatever. I got a good deal on them, and will conduct my own testing on the matter.