I just hope the build quality is better on the new iPhone, in-fact I'd pay double to have a consistent and solid iPhone! I've owned the 3G and 3GS and had replacements for various issues. Only once has the screen been completely level. The one I have now is wonky by at least 1mm, while this isn't worth me getting it replaced, it's shoddy. Same with the gaps by the bezel and uneven seal. I always expected Apple products to be a premium high quality product, the iPhone isn't that in terms of build quality. It's still my favourite phone I've ever owned(possibly favourite ever piece of technology!).
You can't blame Apple I guess, they knock these devices together in a sweat shop full of modern day slaves and sell them for maybe twenty times what it cost to produce them. That's why they are making as much money as they are.
I'd definitely be prepared to pay a lot more for an iPhone if they could guarantee it'd be built better or least if they employed a QC department that were either more strict or knew what they are doing!
From what I have seen of the leaked pictures, if looks like a solid device, it'd be nice if there were no gaps on the new one. I find dust gets in between the bezel and the seal too easily on the current design and is very hard to clean.