I am currently on my replacement V600 which is now acting up.  The first attempt at this and the V600 stopped taking a charge. Sent it back and got a new one. The new V600 is now randomly shutting off, loosing connections, and not recognizing my SIM.  T-Mobile is doing what they can to help me as I love T-mobile, but hate the V600. Luckily the V600 is still under warranty so a return is in it's future, and another phone will come to live with me.