Two iPhone 4S's in my house and zero issues with "build quality"....
Frankly, this is a generation two phone, any issues with build quality should be sorted out by now. Yes there will be issues with a percentage of phones and yes those will be the ones who are most vocal (who creates a thread on a forum just to say "my phone is perfect"?). Apple sold 4 million phones in the first weekend (and who knows how many since). If even 1% of those 4 million have a problem, that's 40,000 phones. There are many, many phones that don't even sell 40,000. Any issues with the iPhone is going to seem magnified due to sheer volume...