+1 to alot of the recent discussion.
I think a cyclocross bike would be a good sweet spot. Perhaps a trailer for better utility on big errands/grocery runs, leaving you with a bike that has 90% of the speed of a road bike with more comfort and durability (and utility - racks, perhaps fenders).

Bikesdirect ti looks tasty
http://www.bikesdirect.com/products/..._pro_ti_xi.htm