my first 3 mons i did both and this is the only one i used, u wont pump much but just when u r going out and leaving the baby with someone, so i would say ya it works fast and if u got to there is also a hand pump to relieve your self when u get to fool and hes not around to do so! and its not big, so i will fit in your hand bag!
FYI I just did the labor and delivery tour at my hospital last night and they said to tell them if we bought a used pump and they will give us free replacement parts for the stuff that should be sterilized ;)