I really liked this chapter. I found Draco's punishment to be very satisfying and I can't wait to see what Voldemort does to him. His plan was an utter failure and he will likely pay for his stupidity and arrogance with his life.
I also want to say I like what you are doing with Snape here. You have actually managed to portray him as a credible spy. This is a feat that J.K. Rowling utterly failed at so you got one up on her, but then again, that isn't saying much considering she thinks he is a hero.
It will be interesting to see the fallout of the events from this chapter play out. What I want to see now is Voldemort's next gambit. So far he hasn't made a move yet, so I am anticipating what his response to the latest events at the school will be.