Having set out my criteria for watching tonight's leaders' debate in today's column, I'll offer a quick rundown as to my evaluation.
Justin Trudeau was by far the weakest of the lot in terms of both depth and flexibility of thought from the very beginning, answering Paul Wells' question about whether he could do more than what was in his party's economic platform by merely reciting talking points about the exact plan which was being challenged. And matters didn't improve for Trudeau throughout: at best he was aware enough to find allies among the other leaders on some points, but he offered little by way of either detail or explanation as the discussion progressed on any issue.
(Meanwhile, his final statement in which his occasional tendency toward word salad gave way to word compost can't be described as much beyond cringe-inducing.)
Elizabeth May was rarely the subject of anybody else's direct challenges, which served to limit her involvement at times but also to allow her to pick her spots. To her credit, she mostly did so to good effect - though it's unclear how and why she managed to completely reverse her position on suppression of democratic governance in the name of trade in the course of a minute between the domestic and international scene.
Rather than playing matters entirely safe, Thomas Mulcair offered more new content than any of the other leaders (including both examples from his experience and memorable lines aimed at Stephen Harper), and found opportunities to work it into the debate. The downside is that it was tough to tell much about Mulcair's response to the unexpected when he didn't face much by way of surprises, but it hardly seems a problem to have been prepared.
Finally, Stephen Harper stuck almost entirely to talking points we've heard dozens of times before (the bulk of which have long since been debunked) and was the lone leader to distinctly fail to acknowledge anybody else's points even on legislation where he had another party's support. At best, one can say that Harper hewed more to the chosen topics and went into slightly more depth than his spokespeople tend to - but that's hardly a ringing endorsement.
In sum, when it came to the leaders' judgment, Trudeau seemed out of his element, May held her own within her chosen niches, Mulcair was thoroughly prepared and Harper appeared isolated in his own bubble. Which is to say that while the debate had its interesting moments, we may have learned less than we might have hoped.