Building a smartphone out of metal introduces all sorts of compromises - not least the way that metals block the very wireless signals that are the lifeblood of a smartphone. People will tell you that the metal feels premium in the hand and that's worth the compromise.
The Verge has an article today on an NPD report that says that 75% of smartphone users and 87% of iPhone users have their phone wrapped up in a case. Personally Id say those figures are on the low side. Other than my own, I can't remember seeing an iPhone that isn't wrapped up in one sort of case or another.
|HTC's Dot Case is plastic, but at least it adds some|
functionality. Apple's silicon case is just awful.
HTC's best phone (as far as materials and design is concerned) is the HTC One X. Nokia's all polycarbonate bodies have been superior to iPhones since the N9 arrived, and the iPhone 5C is probably the nicest iPhone in the hand ever. Samsung's thin plastic backs offer a degree of flexibility that you just don't get in most other premium smartphones, they can be removed, replaced, swapped out for ones with more features (e.g. wireless charging) or ones designed to accomodate even larger batteries.
So, enough with the 'premium build' nonsense. That metal case gives you much, much less, and chances are you'll never know it's there apart from the two minutes it takes you to unbox it.