I have lumia 710 and I agree, the build quality sucks. So I got the 800. Very smooth and responsive. Superb email. Does the basics very well. N9- unreliable, laggy, GPS sucks. Yes, my opinion. And I even bought two N9s, so, yes, I am entitled to my opinion.

N900 is very outdated. Port fell out, but I did like it. In terms of ease of use, lumia 800 beats all of current nokias