I have an in-house framework a part of which is very similar to Boost.Parameter so I tried to refactor it to use Boost.Parameter and, unfortunately, noticed a big compile-time hit (the project has a very large number instantiations of class templates with 'named non-type template parameters'). With my code (and MSVC++ 10) build time was ~56 seconds with a maximum cl.exe memory allocation size of ~720 MB. After switching to Boost.Parameter build time whent to ~2:24 seconds with a maximum cl.exe memory allocation size of ~815 MB. The most likely suspect is the usage of a forward-sequence for parameter type storage (argument packs) from which you fetch passed parameters using key-based lookup with the value_type<> metafunction. In my code I use an associative container (mpl::map) for the task which has a 'natural'/'efficient' key-based lookup... To confirm this I minimally changed the Boost.Parameter-based version of my code only to use mpl::maps instead of Boost.Parameter ArgumentPacks and built time fell to ~58 seconds...(true, this does not have all the compile-time check for correct usage and concept validation that ParameterSpecs and ArgumentPacks have but I'd expect this to have a much smaller effect than key-based lookup on a forward sequence)... Is there an inherent issue that forbids the use of an associative container for ArgumentPacks or can this be fixed? -- "What Huxley teaches is that in the age of advanced technology, spiritual devastation is more likely to come from an enemy with a smiling face than from one whose countenance exudes suspicion and hate." Neil Postman