build quality with nokia is generally fantastic, usually extremely durable, although they are branching out with the 928. it's made of aluminum (like the recent iphones) as opposed to their traditional poly-carbonate, so i cannot vouch for this particular version. one issue with the build quality is dust buildup in the ff camera, that should be resolved in the new version though.
os is fantastic, i love using it, although i do have a few qualms. firstly, the design is top-notch, completely fantastic. supposedly ios7 has even been influenced to the point that their whole redesign is based on the one word that describes wp: flat. lock screen integration is fantastic, i donno how i EVER used a phone without it. however, i don't like that there is no notification center, no easy way to turn the phone to silent, can only toggle between volume and vibrate or volume and silent based on whether your vibrator is turned on (rumored to be fixed in gdr2 update mid-june).
love the "customizability" of the home screen. different from how you customize things on android, but i love the live tiles and the configurations you can build. the biggest complaint is that the app selection is generally weaker as it is not a priority os for developers, but there are still tons of quality apps. i think there is a wp app for android that looks at all the apps on your phone and determines what level of equivalence you would have on wp.
gimme a list of your "must-have" apps and i will let you know if this issue will also be a problem for you.
