Not too bad!
You got the style real nice, but I was kind of hoping the trailer would be longer. Anyway, you've got a good thing going so far. I hope you finish it soon! In the wake of the Portal Collab, a Madness/Portal crossover is only natural. And short of Krinkles himself doing it, you've got the art looking real good.
Protip: Madness is about MOAR VIOLENCE, not beautiful graphics. Granted, the latter makes the former much better, but the cost is something to consider. MOAR VIOLENCE first, then worry about lagging our computers.