When you get to Poznan's Lawica Henryk Wienlawski Airport, you've got a choice. You could haggle for cabs with everyone else, or you could get your stag weekend started properly with a return airport transfer. You won't have to worry about getting to your accommodation in time to check in before you start drinking, and there'll be no chance of taking the wrong connection and ending up miles away from where you need to be.
It's all about organisation. If you don't do it before you go, you've got to do it when you get to Poznan. And who wants to do that? Get your stag party sorted ahead of take-off, and all you've got left to arrange when you arrive in Poland is a round of beers. Your driver takes care of everything else: picking you up off the plane, getting you to your hotel, and coming back to fetch you at the end of the weekend.
Why leave yourself the hassle of finding transport to and from Poznan airport when you've already sorted everything else? Get the coach or minibus booked, and relax. Or splash out on a limo complete with smokin' hot Polish strippers, and start the stag party as you mean to go on!