I was initially very impressed by Eberron for the same reasons many seem to hate it: techno-magic, an apparent complete break with Tolkienesque fantasy, and a (more popular here) WW1-influenced setting.
The incorporation of "everything core" into the setting was the first off-putting element. The core is, at best, a toolbox and at worst a mess. As "D&D," it's at least tolerable because I did once enjoy some of the sacred cows. As a new setting, it gave me fits.
The constant disavowal of technofantasy, steampunk and anything smacking of them was the next step in my lowering opinion. Keith Baker never played a Final Fantasy, and he wants you to know it. Okaaaay. One would think WotC would want to deny a lead designer's ignorance of one of the most influential fantasy series of the past decade, not tout that ignorance. Keith is a great designer and he seems like a great guy, and I wager playing in his original Eberron campaign would be a great experience, but either he or WotC (or both) have some very definite and, in my view, very unfortunate ideas about what is acceptable in a D&D world.
Finally, comparing the core books for Eberron and the Iron Kingdoms made me wince for Eberron. The latter, despite insisting on its own appelation ("Full Metal Fantasy"), presumably out of fear of anti-steampunk sentiment, is a beautiful, cohesive and original setting. Eberron, for all its good points, looks generic, if not anemic, in comparison. Warforged and changelings are interesting in isolation, as are dragonmarks, but are they as interesting as steamjacks, viciously hostile religions, the pain of healing and infernals? No.
The Iron Kingdoms book is hampered by quite possibly the worst crunch I've seen in years - crunch that appears to not even WANT to follow d20 conventions for functions that are by no means original, when it even works - and I'd hesitate to reccomend it, but its flavor is spectacular. Eberron, on the other hand, has some painfully elegant crunch: action points, the artificer class (despite its intense power), some of its races and feats, and basically all the PrCs except Dragonmark Heir, and that only in very specific conditions.
In the end, I just can't get past WotC's desire to straddle the fence on technofantasy: at once they wanted to appeal to a new generation of gamers who appreciate new forms of fantasy (and those of past generations who share that appreciation), but their apparent terror at releasing a setting that dares to offend the sensibilities of those who can't accept this variety seems to have crippled the effort.
In the end, I think Eberron would have been better if either WotC had either stared down the old skool and reminded them that they represent only a single market that a company is entitled to target, or if they'd gone whole-hog with a traditional fantasy setting.
Overall, I'd give it a six.