One huge advantage: if your project already using CMake then you'll be able to include exact version of Boost library into your project as git submodule. Then it's will be built hassle-free across all of your toolchains and platforms.
This will of course require some proper configuration on Boost side, but no doubt they'll handle it.
Well, partly because b2/bjam is aboslutely awful and obtuse, etc. etc.
I did some semi-serious experimenting with it at one point and it was just... well, awful. It basically did very few things right.
(BTW, don't take this as criticism of the authors of said system. I just don't "we" had learned enough and infrastructure was incredibly far behind what we have now. So I don't "blame" them in the least. It's just a product of its time.)
