We just did the MK AH (May 30th) and AK AH (June 4th). We didn't do another park on either of those days, and the day after each we made sure we didn't have any morning plans. We thought MK was totally worth it and we would do that one again in an instant. We were able to get SO much done, including in the two hours before the party actually started since we were able to get three FP). Plus, it was cooler since we were dealing with summer heat. It wasn't nearly as empty as I think it used to be when it first started, but it certainly wasn't bad at all. We didn't attempt 7DMT though since that wait was always 40min when I checked and I didn't want to waste that much time.
While we enjoyed the AK AH, and are glad we did it since this was our first time in Pandora, I don't think we'd do that one again. We really enjoy AK and everything it has to offer, and so much of what we enjoy was closed (animal trials, shows, etc.). We typically spend two days at AK on a normal trip, so AK AH wasn't really a necessity for us. Now, if you only like AK for the "rides", then it's probably more worth it to knock those out.