Well, as you may guess by my handle, I don't have any corns. =)
I do have a little milksnake (well, he's supposed to be a larger species, but he just ain't a big snake) and I've had him on a shelf above my leos for some time. I was using a human heat pad set on low to provide a thermal gradient, and he spent the majority of his time off the heat pad, which was putting the temp around 85-86. When my beardie babies hatched, they were setup on the shelf below him, and with five 60 watt bulbs burning there all the time (note, this is an open wire shelf, so the heat build up isn't too severe), the heat pad was overkill. I turned it off and his ambient temp stayed around 82-84. What I noticed then, is that when it was warmer, he'd spend most of his time curled up by his water bowl, and take an occasional dip in it. Otherwise, he'd spend more time laying stretched out, or under his hide spot.
I think in a larger cage, a warm spot is a good thing, probably necessary, but in a smaller cage (he's a 35" snake in a 24x12 cage) such as this case, perhaps ambient heat has some advantages: Since he doesnt' have to avoid the warm end, he can spend more time stretched out, which helps decrease the chance of respiratory problems, and he tends to soak a little more frequently, which helps keep him hydrated. He can get cooler if he needs to, by hugging his water dish or taking a swim.
On the other hand, you've got leopard geckos, which many people keep the juveniles at ambient temps, and it has been shown that juvenile leos with a thermal gradient grow better.
I think the key thing is to give the animal options. In the case of a snake like the milk, which prefers cooler temps, then a cool off area (porceline water bowl, or as Pro Exotics does, cut a hole in the base of a decorative type water bowl so they can use the base as a cool hide) is a decent option.
How much of this applies to corns, I can't say, of course. =)