I dont practice wing chun myself and cant really comment on the system as a whole but i can say that having sparred and fought with a variety of martial artists of differing backgrounds i have found that i feel the most pressure and have the most difficulty sparring against the ving tsun practitioners at my sifus school(ng family Chinese martial arts association) . That being the case i believe it can be an extremely effective system on the right hands and with the right training.
For what its worth