For the last couple of years I was riding 700x25 Specialized All-Condition Armadillos. When the time came to get new tires, I caved to the Bike Forums peer pressure and decided to try Schwalbe Marathons; 700x28.
These tires are fantastic! They roll so smooth, and it's like the roads just got re-paved yesterday. On my commute there's a road that's particularly chewed up that always rattled my teeth in my head. I made a mental note about a mile prior that I needed to pay close attention on that road to see if I can tell a noticeable difference in the relative "chop" of the ride.
50 yards into that road I remembered that I was supposed to be paying attention. It was that much smoother.
And, believe it or not, they seem to roll faster too. The tires themselves feel lighter, and I used at least one cog smaller on average for every part of my ride than what I usually use.
Two emphatic thumbs up...I'm sold!