I had the opportunity to hear Krugman speak in 2004 before the election. What I found surprising was how much he seemed to value his column. It certainly seemed like he thought it was much more important than his academic work.
I think it's extremely important to have academics in constant communication with the public. Keeps them grounded and their language plain, while the public can continue to engage with academics long after they've graduated.
I can't find any fault in Krugman's academic work. I haven't read it, though it sounds fascinating. He is held in high regard in the academy, and I believe he is as talented as other people say he is.
His NY Times column, however, I feel fit to judge as shrill, unimaginative, vanilla leftism. I'm sure he understands all the criticisms that other economists would level at the policies he supports. The flaws are glaring. Now, it is perfectly honest to acknowledge the existence of those flaws and argue that the benefits of the policy outweigh the drawbacks. However, it is not honest to pretend that such criticisms do not exist.
I could read similar opinion pieces from any leftist without a PHD after his name. The point of reading someone so lettered is that his opinions should be well-argued and therefore interesting, even if you disagree with him. That is rarely the case with Krugman.
I have no doubt that his work in economics will be remembered 50 years from now, and his columns will be long forgot.