Boost is a great example of what a bloated, backward language C++ has become. It relies on complex intricacies from the standard that are difficult for compiler writers to implement correctly and robustly and without bugs. As a result, Boost itself is not very portable. Either it works on your platform and compiler, or it sort of works, or it doesn't.
Boost--and template metaprogramming in general--is a great exercise in intellectual masturbation. They identified a bunch of useful functionality that isn't supported by the language. Rather than design a new language that does support that functionality, or build external tools to provide it, they contort the template semantics of the language in order to try and squeeze that functionality out of nothing.
Well, template metaprograms are crap. They're nigh undebuggable, they produce unreadable error messages, they take forever to compile, and most C++ programmers don't know how to write (or even read) their implementations. They're an abomination.
Since meta-programming is clearly useful, and something that a lot of programmers want to do... why not add true compile-time metaprogramming support to C++ (or better yet, develop a 10x simpler and cleaner language and put proper compile-time metaprogramming support into it)? Templates are not a natural way to express metaprograms. Why not give C++ programmers the tools to write nice, clean, object-oriented, imperative metaprograms instead of the kludgy functional metaprograms they are forced to scrape by with now?
Again: Boost exemplifies everything that's wrong with C++. All of the corner-case features of C++ that Boost exploits in order to provide useful and sane functionality in an insane way, should be removed from the language (or its successor). Instead, general and clean and low-level metaprogramming mechanisms should take their place so that the functionality embodied in Boost could be written directly by any mid-level programmer instead of an elite group of template wankers.
I've got all the money I'll ever need if I die by 4 o'clock. -- Henny Youngman