[tmandry]

I don't have numbers handy, but I can say with confidence that the answer to both questions is "yes". It depends on the use case. Boxing is a useful tool and in many cases the overhead is minimal, but you don't want to use it all the time. Likewise, static inlining can bite you in deeply nested cases and I've heard of this happening too.

The future we're working toward is for this to be a decision you can make locally without introducing compatibility hazards or having to change a bunch of code. Ideally, one day you can even ask the compiler to alert you to potential performance hazards or make reasonable default choices for you...