Starting with the most basic of the three the SGH-A127 is an extremely basic phone that simply has no real place in the market. Currently geared toward AT&T's pre paid customer base for around $80 I'm guessing it is going to be a hard sell condering you can get good unlocked phone with a ton of features for the same money.
Next is the SGH-A517 also an AT&T new phone release that shares many of the RAZR's styling attributes. Fortunately this phone comes with all of the basic features one would expect from a mid level phone. Key features include a 1.3 megapixel , Bluetooth and an expandable memory card slot to store pictures, videos and of course music.
T-Mobile's SGH-T639 is also mid level clamshell phone that sports interchangeable faceplates for those individuals who like to change the look of their phone without voiding their warranty. Key features include a 1.3 megapixel camera with zoom, microSD slot, Bluetooth, MP3 player and EDGE data. Scheduled for release during Q4 of the this year.
Look for full specs and images to be available soon.