There's a(n) Halachah (citation help, anyone?) that you are not supposed to pass in front of someone in prayer. As a result, many people are strict and won't take their three steps back when finishing prayer if there is someone praying behind them who hasn't finished yet.
A) How strict should you be in this situation? If someone immediately behind you began Shemoneh 'Esreh late and therefore is still near the beginning when you finish, do you really just have to stand there until he finishes? Do the people in front of you have to also (because you haven't completely finished)?
B) If the congregation continues forward with Tefillah are you allowed to continue with them even though you haven't taken your steps back and said 'Oseh Shalom, etc.?