Best clincher... ever.
I have put about 2500 miles on a pair of 23's, and I am in love. They are responsive, tough,and FAST (noticeably fast). They climb well, roll smooth on the flats, and are confidence inspiring on the downs. Great for commuting, training, and race day.
The 4000's are the best tire for the money, hands down. Stay away from Michelin and Vitorria, just stick with ze-Germanz for an amazing and honest tire.