I've been rolling 700x30c (28.5mm) Kenda Kwicks since I got my 'cross bike in May 2008. Only one flat to speak of. Tires still have plenty of tread. I've had them at 50 psi (I'm 150 lbs.) on the streets to soak up road chatter. They're rated at 60-85 psi. Nashbar usually has these tires for cheap.

I will never make my cyclocross bike wear slicks! It's like trying to make your son wear a dress. It doesn't make sense. Wait for a daughter (or road bike). Not that I have anything against road bikes. I've had my share.