Update (8:30 p.m.) below.
Probably the best read on last night's Munk debate in Toronto that you will find: "Krugman vs Summers: The debate." Felix Salmon, the great blogger at Reuters, was here for the event. Salmon, who can make even the topic of online advertising interesting, sums it up in his unique way. As a bit of a spoiler though, you'll see that the optimistic view prevailed on the question of whether “North America faces a Japan-style era of high unemployment and slow growth.”
Update: Krugman's brief take on the debate that is out tonight, linking to Salmon and clearing up the characterization of him as a pessimist: "Larry and Paul and Dave and Ian." (h/t)