In an ideal world these should be two seperate magazines; Dungeon concentrating on 3.5e and Polyhedron covering all other aspects of d20 gaming. That would be my prefered option as it would mean I could stop buying a large chunk of information I have never used (Dungeon). However we don't live in an ideal world and to get the articles I want I must buy the combined magazine.
I had a Dungeon subscription from about issue 70 through to the start of 3e coverage (present from the RPGA), the problem was that the majority of the people in my group also recevied Dungeon magazine. As result we have never run a singe adventure within its covers, it is the same problem we have had with any published adventures.
In the good old days of OD&D / 1e it was different. In the UK getting hold of gaming materials was more difficult, most of the players were at school, had little income and (for teenagers) to get to any shop that sold gaming material involved a high level of pre-planing. In reaility this meant that the GM (with a job and car) was the only one that had the ability to purchase adventures.
I don't play 3e/3.5e anymore, GM boredom and general anonyance with people that telling me what can and can not be in a DnD game. I play the mini-games, d20 modern and third party non-fantasy d20 as well as other systems. The mini games showcase what can be done with the d20 system, Hijinx was much discussed and praised on the likes of RPG.net, an site that doesn't tend to talk up the d20 system.
These days I think long and hard about purchasing Dragon or Dungeon, there has to be something of value in them. Dragon I am currently only buying for the Ebberron previews (a world that may, in the long run, bring me back to fantasy) , Dungeon for the mini-games and d20 bits. If an issue is sealed I don't buy it and I have a FLGS that will put back copies of each for me on spec and if I don't want it on the shelf it goes.
That said, I understand that Paizo is a company and MUST make a profit if it is to survive. To make a profit it has to go with what the majority of its readership wants and if I am not in the majority then OK, I'm married, I'm used to it, I'll move on.
Pax.