Compile times are really important for productivity. I would abandon an engine immediately if fastest test builds took over a minute. 40 seconds from modification to testing is still bad. One of my software engineer friends has told me that even going from 30 seconds to 5 seconds is enough that it's a significant factor in his choice of programming language for a new project (and he's not in games; the iteration time is more important for us than him IMO).
This is why I really like Unreal Engine 4 atm. You can create something really fast in Blueprint (prototype, testing, etc). And when its stable you can re-make it in a C++ class for the speed and efficiency.