I don't feel I am the exception actually... I hear the same complaint uttered over and over. My brother collects this line die-hard (I pick up one here and there), and he's got the same gripe about how they execute a great figure but stick a crappy head on it.
The Gondorian Ranger and Rohan soldier are the 2 most noteable I can think of off-hand though, but I've heard a new Rohan Sooldier's in the works? I'd be happy to see that... Hell, just seeing the old one with hopes of customizing it would make lots of people happy.
Beyond that, the only gripe about Army Buliders has been a lack of them shipping. They're not always easy to come by I've noticed, though some are reshipping like the Uruk Hai Crossbowman, which is a great figure.
I do look at things closely, but my gripe's one that I'm hearing a lot... And at the same time it may be something that the company's trying to alleviate too if that 2nd Rohan rider's to come about.
Beyond that I think this line's great, even with action features sometimes. I mean, my Uruk Hai Crossbowman's feature sorta works even. Can't complain there.
The one MAJOR gripe I have with the line is the scale, only because i too agree that I dislike 6" as far as displaying. The price drop's helped with even buying the random figure though. I'd like to have seen this line done in 3.75" though... To me you'd have been better off with the grand scale of the films. Play environments and large beasts just aren't feasible all the time in the scale it's currently in, whereas a 3.75"/1:18 line would've yielded a Balrog long ago, and the possibility of many other creatures and sets like a Helm's Deep even.
The little AoME line doesn't make up the differenence either. It's really sad in comparison.
Beyond that, I don't see many gripes about the line... No substantial ones really anyway. The odd "This sculpt sucks" leaks out though, and some of their repacking seems questionable. That's all toy lines anymore though.