What's New, Beelzebub? is definitely a great ending for a great season. While it has taken the writers and designers a while to find their comfort level with this version of Sam and Max, the last two episodes show that they've really firing on all cylinders. The overall corporate atmosphere of Hell and the characterization of Satan are hilarious and, better still, the actual content of the episode ties up the first two seasons very nicely.
The puzzles aren't quite as challenging or rewarding as they were in Chariot of the Dogs but that's a minor criticism, because they're still very good overall. IGN did like the small hints at further episodes to come but, honestly, after a season that went from Santa's Workshop to a zombie rave to outer space to Hell, the designers are really going to have a hard time topping themselves.