The button-issue you talk about is actually intriguing me. When I first looked at the 950/950XL in the MS store in NY I thought exactly the same thing as you. They didn't feel that great and were a bit "wobbly". Since the 950 was on sale and my Android LG G2X was borderline unusable I figured I'd pull the trigger on a new phone anyway. To my pleasant surprise my phone has buttons that are totally fine. The feel solid and not "wobbly" at all, and there isn't any "clickyness" to them that bothers me. Neither does the back 'creak'.
So all of this makes me wonder just what's going on. I mean, could it be that some are selling refurb devices without disclosing it, and that prior users handled the phones carelessly? Or is it poor QC where some batches are bad and some are good? Or is it that users just handle the phones differently and get different experiences?