I have kept my baby corns without gradient last summer, and they did fine. But I keep my adult corns and kings at 86-90 hotspot, with the cool side being 65-75 (depending on day or night) and likewise they have done well, but these snakes utilize the cool area for sure, normally a few days after a meal/sitting on the heat.
I think for colubrids generalized heating works fine gradient or no...they are forgiving. But I doubt I would be keeping anything else without a better level of control on temps....definitly not if I was looking for breeding sucess etc just because controlled hot spots and cool sides automatically knock out any problems that could arise from less controlled heating methods (i.e. whole room heating) But then again, I have never bred pythons or boas, so my experience in that arena is worth nill. Just an opinion.