Pros: Reliable, very compact
The 3120b is a very basic candybar phone. The keypad has nice "clicky" buttons and the phone is easy to navigate. The display screen, though low-res at 128 x 128, is clear and useful. The phone's menus are easy to navigate.
I obtained this phone a few years ago in a Cingular refurb deal and was able to unlock it online.
The phone has no camera and no speacial features other than reliability and ease of use. I keep it in my bag in case my normal AT&T phone battery goes dead. A SIM-swap into the Nokia and I am good to go until I can recharge.