Of course, now I had to go read all the recent yelp reviews...they are so much fun to read although I typically stick to tripadvisor. Every review needs to be taken with a grain of salt. As people have said - most people - over 99% do not leave reviews at all. Those that do typically had a fantastic or terrible experience - hence the multitude of one and five star reviews and few three stars. Even though I know these reviews are full of hyperbole both ways, I think you can always get a good feel from reading them.
From what I can gather about the one star reviews of Disneyland Hotel - they are based on the cost, fact that the monorail wasn't running, pool problems, crowds in the Parks, or no complimentary breakfast. Actually that was the most common one - people complained that there was no complimentary breakfast given the price. Most of the chain hotels (Hamptons, etc.) offer complimentary breakfast, but most independent ones or pricier ones do not. Personally I hate that free breakfast, but I don't have kids and understand that it can be a real cost saver to those families who are used to it when traveling. Most of the other reasons for the one star were out of control of the hotel - but there were some valid complaints about some minor wear-and-tear in rooms. Overall though, I wouldn't take the one star reviews too seriously.
Enjoy the ambience of the beautiful hotel and enjoy every second of your vacation (and buy a Mickey waffle for breakfast