I haven't use Loki but I've actively used boost on my previous work. Boost has implemented many ideas from this nice book;
Things from this book are not intended for use in Business Logic, they should be implemented in libraries (Boost, Loki, something of your own) and libraries used in Business Logic. This is a different thing "using this tricks in code" or "implement separated library with using this trick and using beautiful libraries in most of your code (for example boost::bind - ugly implementation but nice in usage - but you almost never see this implementation)"
Also this book demonstrates powerful c++ meta-programming and good training for brain.
