I didn't like that they said it wouldn't raise prices
I didn't like it because they said it wouldn't raise prices and then a little while later raised prices because of increase printing costs. I dropped my subscription almost immediatly. I liked dungeon better when it wasn't glossy as well. It may look better, but it was more functional when you could write on the pages in pencil. I don't tend to show the players much of the magazine, so the color art and backgrounds only server to drive up the price and make it harder to read and use.
I also feel that the types of adventures they publish have gone away from what they did so well in the 80's and early 90's. It used to be that you could find small adventures that would fit into almost any type of campaign world. Now the adventures all seem very dark and epic. That's fine if that's your style, but if not, it is much harder to use the module. I also felt that the quality control of the modules has gone way down in the last 5 or so years. I don't get the feeling that the modules now are always written by experienced GM's. The plots involve more railroading and less player involvement than they used too.
It used to be that we would eventually play around 75% of the modules in any given issue. The last couple years I felt lucky to pluck one module out and use it. Instead of being a GM aid, it became more just an excuse to get money from me for marketing their games to me. I tried to give the new guys a chance, but it just wasn't worth the money, so I dropped my subscription after getting Dungeon for close to 15 years.
As for Ployheadron. I didn't hate it, but I rarely found it usefull.