I have read up on this and heard the same from owners. I also witness my coastal's activity level.
Scrubs, Olives, and Water pythons are all quite active.
Not colubrid level, but as far as pythons go they are busy.
Folks on the Aussie boards think the scrubs are very similar to the retics.
I also agree with Josh, being "active" isn't really a measure of intelligence.
A boa constrictor will find an animal trail and set up camp and lie motionless. There is a study that I can't find at the moment where a BC was observed for 3 months in the same spot.
It could be considered intelligent hunting, or maybe not. However one determines "measurable intelligence" in specific snakes still a ways off.
There is an inconclusive study in THE BIOLOGY OF BOA AND PYTHONS book that was preformed on carpet pythons. The scientists did not get the results they were after and needed more time and more specimens.
I'm betting there are more studies out there or in the works, but for the most part, they are all pretty hardwired the same with the exception of maybe the "lesser" blind snakes or thread snakes that are the most primitive.
The King Cobra is supposed to be the most advanced I believe.