Even though it is permanently closed it is still kept up and a great place to stop, especially if you're a Disney fan! Great and fun photo op!
We just went for the first time the other day. Besides having to wait for daycampers to go by so we could see anything, it was one of the best zoos we have been to! Best to go early and beat the heat if you can and take a lot of water or a container to fill up. Good walking shoes are recommended as well since you will walk 5 miles or more if you do the whole zoo.
The tour is a lot of fun and you learn a lot of interesting things about Seattle that you wouldn't have normally known. The tour I believe when I took it 10 years ago used to be longer and you didn't end up in a gift shop, but the shop is very cute. My 7 year old son loved it! However, my 6 year old girl was totally creeped out but I think that was more of the closed in spaces and the large group (about 15 people). If you come to Seattle, if there is one thing that you do... This would be highly recommended that you don't miss.