For my family, we love AK. We can easily spend 1.5 to 2 days there. However, for every family you find who loves it, you will find another who says they can barely find enough to do in half a day there. It is really going to depend on your family's personal interests.
We like zoos and anquariums in my family. We like exploring the animal trails. We like doing all the craft/activity booths that are part of the Wilderness Explorers Program. These things alone can take a day by themselves.
As far as attractions, we enjoy in order of preference:
Festival of the Lion King Show
Everest Coaster
Dinosaur ride
kilimanjaro-safaris
It's Tough to Be a Bug show
We also really love the buffet at Tusker House.
Personally, we feel it is worth it because we are invested in all AK has to offer (animals, rides, shows, restaurants, theming, shopping, street performers, education, and games and activities). We get there at rope drop and stay until closing, and we always end up with things we cant fit in. I think most of the family enjoy the animal viewing and educational activity booths as much or more than the actual rides. But my family's kind of weird I guess. Our first trip to Disney, Epcot was everyone's favorite park, followed by AK.
If we were only interested in experiencing a few attractions, I don't know that AK would be worth it.
AK's theming is primarily African, Asian, Animal, Dino, and Education/Conservation inspired. If these themes appeal to you, you will probably enjoy it. If you don't care for these themes, or don't really care about learning on vacation, it's probably not the place for you, at least not for a full day.
My suggestion would be to ask yourself these questions:
1. Do we want a "zoo" experience? Will we care about taking time to see the animals? If yes, you will want at least 2-4 hrs for the animal viewing trails alone. If you are content with your local zoo, and want something different while on vacation, this may not be the park for you.
2. Is anyone interested in a petting zoo? If yes, give yourself 1.5 to 2 hrs for this. You have to take a train to the island where the petting zoo is, walk down a path, and then do the reverse to get back, so it can easily end up taking 30minutes one way, depending on how fast you walk and how long you have to wait for the train. Also, in this area you will find a veterinary area where they perform procedures on the animals at different times during the day. If this interests anyone, it may be another reason that AK might be worth it.
3. Do we care about participating in the Wilderness Exploreres Program ? (free educational activity booths where you earn badges based on the group in the movie UP) There are 32 different badges to be earned. It can take anywhere from 3-5 hrs just to complete these. However, you are free to collect as few or as many as you wish. We've never had enough time to fit in more than a handful each day.
4. Do you like African / Asian themed architecture, restaurants, shops, etc ? If not, you probably aren't going to enjoy the atmosphere, shopping, or food very much. If you are a big fan, you may want to spend extra time watching the street performers or window shopping.
5. Do you care about eating at any of the sit down restaurants ? ( Rainforest Cafe, Tusker House, Tiffins, Yak and Yeti) Personally, we don't care about eating at the Rainforest Cafe because we have a local one we can eat at anytime. However, I think it's definitely worth going at least once for the atmosphere if you've never been, especially if you have kids. We love Tusker House because the food is so different from everywhere else at Disney, and we love that the buffet style allows us and the kids to be more adventurous and try new things without the worry that we won't like what we order. We also love the Jungle Juice and the character lead parade is fun for kids.
6. How many attractions is your family actually interested in experiencing? Look them up. Make a list. Do you think you may want repeat rides on anything? For us, we probably spend about half the day on the rides and shows listed above and the rest of the day gets taken up by everything else. We usually ride Everest and Dino a few times each and the Safari ride twice. The shows we only see once. Then depending on who is with us on the trip we may do a few other rides or shows as well or let the kids play in the Boneyard play area or in the Dino carnival area. You can use a website like Touring Plans to estimate the time needed to see the attractions you choose. This will help give you a better idea of how much time to plan for AK if you do go, and if seeing only those attractions is worth eating up that much time.
7. Are you interested in carnival type games? Are you ok with forking out extra money to let the family play them? If this interests you, then there is a whole section for you to enjoy. If not, it's pretty easy to avoid this section. Personally, I'm not paying more money when there are plenty of free things to do, but I've gone with friends before who enjoy this section a lot.
8. Are you ok with lots and lots of walking? AK is huge, and the attractions are spaced far apart. On top of that, to actually view the animals requires even more walking on the viewing trails, with the exception of the Safari animals which can be seen on the ride.
Once you answer the above, it should be fairly easy to sit down and make out a list of pros and cons and what you might want to see and do. From there, you should be able to tell if you feel your list justifies going or not.
Good luck with whatever you decide.
