Ditto! I have booked my flights exclusively with points for the past 3-4 years. I've lost track of how many times I've gotten points returned when a price goes down or changed flights when plans go haywire. And I'm much more likely to pull the trigger on buying a flight early when I know that how it easy to change this if need be so, in the end, I know that I'm getting the lowest price possible.
However, the first time that you have to let a flight credit expire because you can't use it, any potential "savings" is likely gone. How many people got stuck or risked getting stuck in the past year? Also, I often book flights for my traveling companions and, if their flight goes down in price or they can't go for some reason, I get my points back rather than them getting a flight credit that only they can use.
Note: I never buy points at full cost. I always wait for them to offer me some sort of deal (last spring I was getting insane deals of 40-70% additional points) which makes the math closer to even.