I have run 1" slicks - Hitchinson Air Lite Pros in summer and a Tioga City Slicker on the front right now. Fast, hard, nice roadie ride. The Hutches are very delicate and puncture like mad, but that's the trade-off for such a gracile tyre.
A 1" front, 1.25" rear combo is good for commuters: fast precise handling, but a little more comfort.