I think the main reason that a lot of Paizo fans like the crazy gonzo stuff more than the traditional (myself included) is that, well, I've got tons of traditional fantasy modules. There are just way more traditional modules in print for 3e, Pathfinder, and D&D in general than crazy stuff like Iron Gods. Frankly, there aren't more sci-fi D&D like products then fantasy ones, not by a long shot, and there's even less science-fantasy. While I, and I think most people, don't want everything to be as out there as Iron Gods, there's a definite demand for the crazy. Just look at how well Distant Worlds sold and is regarded, or the excitement for Iron Gods. I understand it's not for everyone, but that's not a bad thing.
On another note, the thing that disappoints me personally about Iron Gods is that it seems to be playing things very safe. Almost every AP has done something that sets it apart from other adventures. Jade Regent dealt with eastern mythology, Kingmaker was a sandbox, Wrath of the Righteous used mythic rules, etc. Even Shattered Star, which is almost entirely dungeons of various kinds, had the twist of being the first Paizo AP that dealt with previous AP's and their effect on canon. I'm just not seeing anything like that here. And maybe that's what Paizo is going for, I don't know. But this sort of story has been done so much (heck, Paizo themselves has told a very similar story, with Rise of the Runelords) that it just seems unnecessary to retell it without adding something.
But to be more positive, I am excited to see more of Belkzen, though I don't know how much of the AP takes place there. And despite my grievances, I'm sure Paizo will do some great stuff in this AP, per usual, but I just feel Paizo's efforts would be better spent on more unusual campaigns. But that's just me. And who knows? Maybe this will be the best AP ever and I do a total opinion 180. I certainly wouldn't mind that.