Transformers is supremely profitable, that doesn't necessitate quality though.
Interesting point bringing up Transformers--because that is a high-quality attraction even though it's a popular IP and not original.
I'm a moderate fan of TWD (only seen the first two seasons because that's all that's been on Netflix and I don't care to watch it on real TV) and thought last year's house was ok. I've also been going to HHN since 2007 so I've seen what they can do with heavy IP usage (2007, 2009, 2012) and going all-out original (2008, 2010, 2011)...with the exception of last year, I have always had a blast, original or not. Because even though they may be going for the IP's more and more nowadays, we can't deny that A&D still puts on a hell of an event--it's not like they all of a sudden forgot how to make stunning houses. They've just gone a different direction.
I personally prefer originality over IP's (not just in haunted houses, but for any theme park attraction really), but that's generally because I like buying into a new story and not knowing what to expect--it makes it easier to get enveloped and immersed into the attraction. That being said, that doesn't necessarily mean that IP attractions are bad. Transformers, for instance, is easily one of my favorite rides in the resort now, and it isn't original. Some of my favorite houses in the past have been based on IP's (loved Camp Blood, Dead Silence, Flesh Wounds, Silver Screams, and didn't mind most of the others), because I don't go into a house expecting not to like it just because it's based off of something else. In addition, I loved Interstellar Terror, Saws n Steam, Psychoscareapy, and Hades even though those all borrow heavily from outside sources (nobody seems to complain that those all seemed unofficially based off Event Horizon, '80's dystopian movies, Black Christmas, and Greek mythology, respectively). Is it nice to be immersed into an original story? Of course! But does A&D all of a sudden not take the same amount of time and care into developing houses that they haven't created the backstories for themselves? No. HHN has always been a quality event, and always will be. The sets will still be impressive, the effects will still be stunning, and the scares will still be there no matter what (last year was an exception, but I feel HHN wasn't Universal's priority that year so it can get a slide).
If the theme of this year was Jack the Clown's Zombie Circus, would we all like it better? Even if the sets and themes were exactly the same? TWD does lend itself well to haunt material, and we will probably see some stunning houses this year no matter what. Furthermore, we've seen some stinkers that have been completely original (The Spawning, Reflections of Fear). I think that IP or not, the quality will always be consistent. Yes, the added crowds suck. Yes, we will all miss being lost in the intricate stories HHN used to develop us in. But in the end, what matters is that we get a high quality haunt event right? Does anyone remember Bloody Mary's patients, or the date of Julien Browning's suicide? No. But do we all remember how friggen awesome Dead Exposure was, or how innovative the In-Between was? We sure do. As long as the quality is still there, I don't think the IP usage matters. It's regrettable that the event has moved in that direction, but not the end of the world. In the end, TWD does offer a lot of opportunities for some very cool set-pieces and designs, and I won't not enjoy them just because they came from a television show.