It doesn't matter if Quicksilver can technically run into a room, punch every occupant 20 times and run out before anyone notices... he must still pose his moves as an attempt. The defender, in turn will react in accordance with his/her IC abilities. So yes, if you have the speed of a normal individual, chances are you will get hit, the actual choice is yours but you must play with your IC limits in mind. How much damage you take is also your call based on the attackers +powers and pose, but it is not to be dictated by the attacker against your will. Ever.

Always keep in mind consequences and results. If you're standing on stairs and you've posed taking a hit to the head, you'll probably stumble or fall down. If you've broken your leg, you most likely will not be able to sprint across the lobby and leap. If a normal human falls from a great height, they tend to be in pain. etc. Remember what has happened to you, it's your responsibility to keep track.

Also keep in mind positioning. Look at the environment. Look at the characters involved. If Guido is stooping in a room with a 5 foot ceiling, don't be posing a flying jumpkick or a leap (at least without hitting your head). Try and picture the scene, and it should be obvious certain things will not work. If a fight is taking place in a narrow hallway, chances are you won't be able to slip past each other. In terms of surroundings, if an explosive fight is taking place in a shopping mall during Christmas season, there will be bystanders.