I don't ride thinner than 28's anymore, period. I commute on 38's now, but 32's have been great for me in the past. Even many race teams are moving away from 23mm tires now and riding 25's.

Contrary to what someone said above, it's actually thinner, higher pressure tires that are more prone to flats, mainly due to the high pressures required. I find wider tires when properly inflated to be more comfortable, faster, and more flat-resistant than thinner tires.