They do look cool Plus, I agree! Perhaps a sloped ramp might be handy when introducing a swarm to its new home hive location? But even still, personally I do fine without it in this case too. I use a piece of plywood laid against the two inch lip that I described earlier, for that purpose. Which by the way, another good advantage for the two inch lip or 'landing area' if you will, in my opinion.
Please do not misunderstand me, I am not advocating 'for, nor against' a sloped entrance. A beekeeper should do waterever works best for them and their program, per their methods of beekeeping. Experience is a wonderful teacher and there is more than one successful way of doing things in beekeeping.
Phillip