We also belong to that group of people who love AK. DH, DS (10), DD(7) and I think it's great. That says a lot coming from DD, because she normally makes a point of hating things that her brother likes, and he's seriously into animals. We arrive at AK at opening and leave 1/2 hour after closing and still have a few things that we were unable to tackle during the day. We must be moving at a pathetically slow pace! I would agree, however, with jann1033 who said that it's more of a specialized park, so if you're not excited by animals in general, I can see that it might be less interesting than the other parks.
We ideally spend 2 days each at Epcot and MK and 1 1/2 days each at MGM and AK in order to see most of the attractions. Every time I hear people calling AK a half day park, I think "OMG, what are those people missing?". I certainly don't mean to offend anyone on this thread, or on the DIS, but I guess it's just a case of different strokes. I could make any of the parks a 1/2 day park, by selecting just a few top attractions. I think, though, that if I stormed through MK and hit only Space Mountian, Buzz, Splash, Big Thunder and Haunted Mansion I would enjoy my morning, but I sure would have missed a lot!