I used the DVX in like upper 20's with no problem. You really have to be careful though, otherwise condensation can form inside the camera. To prevent this, when bringing the cam from a warm environment to a cold, and vice versa, let it remain closed in its case for 15-20 minutes so that it can "adjust" to the cold, this will also help to prevent your lense from fogging up. As for the tapes, the Panasonic MQ tapes are the best, and most recommended for the camera. I just purchased some at www.tapestockonline.com for around $5.40 per tape.
