I think having any new phone that turns out to have issues (either software or hardware related) is more often than not just down to bad luck. I've been a wp user for a few years, starting with the htc7 trophy, the lumia 800 and now the 1520 and I've had a pretty good run (apart from a small screen issue with the 1520, which was replaced immediately by my carrier).
In contrast, my wife has had an iphone3, iphone3, iphone4s and now a 5s........and every single one apart from the 5s has had problems ranging from screen damage to software corruption and intense call dropping/call signal issues, not to mention some really bad scratching on the back and sides.
Bottom line, I think Nokia, HTC and most of the other manufacturers generally make really high quality phones, but inevitably I would estimate that at least a few hundred in every million has the potential to be a "problem phone"