After reading the referece docs I got the impression that the only difference between io_service::post and deadline_timer::async_wait is the fact that the former triggers execution immediately (after the caller function returns?) while the latter waits until timer expires before execution of the function object.

io_service::post() asyncronously executes a functor in one the threads running io_service::run deadline_timer::async_wait() ansyncronously waits until the timer is expired or cancelled, then executes its handler in one the threads running io_service::run