I think Zippy batteries are great. I've had the best luck with them out of all the inexpensive lipo batteries. I just bought 3 of these, they are great. They are at 3.8 volts at 4.5 minutes of sport flying (I'm still breaking them in) They come down just warm to the touch.
BUT..... I would have given 5 stars across the board, but one of the 3 I purchased takes 50pcnt longer to charge than the other two. Obviously once cell is slow to charge. For the price I'll live with the issue, seems that once in awhile a Zippy comes with something wrong.