I've increasingly a fan of larger tires. I have 32c's on my commuter bike, and find that it's much safer to be watching traffic than to be constantly watching the pavement to avoid cracks and potholes.

I also just increased the size of the tires on my long-distance bike (the Davidson in my sig line) to 28c's from 25c. A lot of the riding I do w/that bike is out in the hills and mountains; frequently there is gravel on the edge of the road and pavement problems...it now feels more stable and sure-footed than it did with 25c's.

I've also been reading "Bicycle Quarterly", including a bunch of back issues; the editor (a very accomplished and fast randoneer) has been systematically testing wider perfromance tires and is a big advocate of bigger tires for fast, long-distance riding. If you're really interested in the topic it's worth getting some of their back issues where they explore the benefits of wider tires (wider = 32c and 35c).