I wouldn't exactly say Tim Cook's "shit-talking" it. His quote from D11 on Glass is:

"There are some positives in the product. It's probably likely to appeal to certain vertical markets. The likelihood that it has broad appeals is hard to see."

I think that's actually a fairly well-balanced statement. He also says this about glasses and watches:

"Nothing that's going to convince a kid that's never worn glasses or a band or a watch or whatever to wear one. At least I haven't seen it. So there's lots of things to solve in this space."

This isn't saying that Glass will never work or that it's a bad idea, just that as it currently stands it needs a lot of work to have a mass appeal, which is probably true. I, for one, am looking forward to see what Glass becomes in two or three iterations time.