A lot of research has gone into discovering whether a skinny high psi tyre is actually any faster than a wider tyre of the same composition and most people are surprised, (and a few are still in denial), to find that wider tyres actually roll out better and much of the speed you get out of skinny high psi tyres is a misperception.

The only advantage a 23 has over a comparable 28 is a small edge in aerodynamics and the slightly wider and higher volume tyre will offer an improved ride and better handling.

The construction of a tyre has more to do with how fast it is and how well a tyre rolls is based partly on the stiffness / deformation qualities of the sidewalls and how well they pass over small obstacles... too much psi will reduce a tyres ability to absorb the small imperfections and debris we ride over and can have a negative effect on handling and performance.

When you set your air pressure your tyres should deform / compress by about 10% of their depth when you are on the bike, heavier riders will need more psi while lighter riders should use lower pressures to get the same compression.

So with all that being said... I have been riding a set of 700:23 Continental Ultra Sport Kevlar tyres for well over a season on my fixed gear road bike and despite their narrow width and fact I do run them at 100 psi (120 psi is max) they have an awesome ride quality and are exceptionally fast.

I usually run 25-28's on my geared road bike and my hybrid runs some 700/35 Schwalbe cross tyres that I find to roll out better than Marathons as they are lighter and have some decent puncture protection... my last set of these went 8000 km without a flat and are still in daily use.