I can't imagine a C++11 implementation of meaningful compile-time query checking. C++11 and 'constexpr' is like a toddler at doing maths.
Please don't get me wrong - I appreciate every effort to improve the library landscape. But if the bar is that low I have a hard time seeing the benefit of this library given that there's sql11 out there for years.
The main benefit of this library is providing the user an async API (plus being compatible with any user code already using Asio). The licensing also differs. sqlpp11 is a different kind of library: higher abstraction level, provides uniform access to different SQL flavors. It does not provide any async API though. If it did, Boost.MySQL could be used by sqlpp11 as a backend to access MySQL. What I mean is that I don't think that higher level libraries (like sqlpp11 or any ORM) are competitors, but can build on top of this library, instead.