We've been playing with a C79 recently, and let's get this conversation off on the right foot: it's a value phone. Yes, MetroPCS charges $159 for it, but that's completely contract-free with no strings attached, so realistically it'd run just a few bucks if the carrier were to offer it on a two-year deal (which they don't). That being said, this is a case where you get what you pay for -- the C79 feels like a cheap phone through and through. Paradoxically, it's both bulky and uncomfortably light, which definitely contributes to that. The external music controls are weird and unnecessarily small, and while we could really juice the volume on the earpiece during calls, the sound was pretty muddy. On the plus side, the keypad is awesome with large, easy-to-press buttons that even the fattest fingers would have no trouble using, and the screens are bright and reasonably colorful (though the 220 x 176 resolution never lets you forget that you're dealing with a lower-end device here). We also had no problem with the hinge, which is a component that's always at risk of cheesiness when you're dealing with inexpensive hardware -- it felt solid and consistently closed with a satisfying, positive action.
With a couple midrange features like microSD expansion and stereo Bluetooth included, we could reasonably see picking this up if it were offered to us for free on contract -- but paying just shy for $160 out of pocket for the C79 is a tough pill to swallow. Then again, when you put things in perspective, ZTE's a brand new player in this market and this phone is a strong early effort. Needless to say, the established players would definitely be wise to keep their eyes over their shoulders over the next couple years.