I don't even know many racers who go skinnier than 23s. The Specialized tires do seem to get a bit wide after very little wear (they LOOK more like 25s). There are much better tires for tight and/or wet cornering and racing, but the Spec'd tires are really really durable, and, again, if you don't race, there isn't much need to go with a pricier tire with a shorter life.

I've been told by friends that the best of both worlds for durability and performance are the Conti 4000 series tires. I've been happy with my Michelin Race tires (so much better for racing than Spec'd, except for maybe the open tubulars), but they don't last as long.

I would not go skinnier. The skinnier the tire, the more you are prone to wiping out for bumps, and you have less cornering surface. They are the most useful on the track, but not really worth it on the road, particularly if you're not racing, and I think even road racers tend to stick with 20s at a minimum.