it never hurts to add a few days onto the start/end of the visa.

as for "I also wonder whether arriving after or leaving before the specified dates would also result in some bureaucratic hassle." if you mean arriving/leavie before/after the dates on the visa then YES, PROBLEM.

you will not be able to enter (and probably not even be allow to board the aircraft) if your visa is not yet valid. and if you try to leave with an expired visa you will be turned back at passport control and told to organize an "exit visa" which is a hassle. (it is possible to do at the airport directly with a consul stationed there- but getting it is unreliable and unpredictable.) so you are much better off adding extra days onto your visa application. the embassy staff wont even question it.