I love my Masters, even the 23's run nice and smooth, in fact just as smooth on decent roads as my big tired bikes (but not as smooth over potholes and large cracks). Only gripe since I got the colored ones is keeping them clean. They now seem to be permanently dingy lookin. Any tricks?
I've got some 25's too but haven't tried them yet.
Only other relatively skinny tires I have ridden that were nearly as nice in gum walls are my Conti Classics (25s). Those seem to be very nice if the darker gum walls work for you.