Well, there's no way you can make such a list without incurring bitter disagreement. Probably it is a mark of the extraordinary quality of the Smiths that there is such a wide variety of views on best/worst songs. There are very few songs that does not crop up at least occasionally when people name their favorites.
Personally I disagree the most with his underrated list. There's not a single song on it that doesn't deserve to be regarded as among the weakest of the Smiths production, save for Still Ill, and I can't see how that is underrated - on the contrary, it seems to be a regular fixture on most fans' favorites lists.
Among the overrated I would include Reel around the Fountain, The Headmaster Ritual (good, but not that good), Rubber Ring, Sheila Take a Bow, The Queen is Dead and everything on Strangeways.
Underrated: Suffer Little children, This night has opened my eyes, These things take time, Girl Afraid, Stretch out and wait, Ask, Jeane, Wonderful woman and well I wonder.
cheers