I've been riding on Marathon Slicks for awhile on my Swift, and found them to be fast but too harsh - even at lower PSI's. So, I'm giving the Marathon Racers a shot.
So far they're very comfortable, albeit a little bit bouncey. They also don't feel as fast as the Slicks (not surprising, since they're wider, have more tread and a lower PSI). And yet Schwalbe is billing them as "the fastest Marathon ever."
Anyone else using Racers yet...?