i find it lovely when i need to compile boost, its almost like its made for you to not compile it or anything that uses it, use a source based distribution and you'll be as angry as me
The longest emerge I've had on Gentoo, besides possibly the hundred-or-so dependencies of X, was actually pypy. I have Boost installed, but I can't honestly remember emerging it, which is to say, it had to have been painless.
quite frankly xorg was painless to install, however i keep it as lean as possible, Ill get back to you on this. Haven't compiled pypy but the longest i've gotten is firefox which i gave up on because after a couple of hours it maxed out the swap! should've paid attention to the notice of "you cant compile on anything with less than 1gb ram"