+1 on the zippys. They perform great for the money. Like JHautz said, I am going to have a hard time buying another one of the name brand packs. I race my buggy with the Zippy 5s 4000 & 5000 packs and have a couple of 4s 5000 packs. Plenty of power and I can't really tell the difference between the zippys and the enerland based packs I have.

The zippy's aren't built as well as I had a couple of bad solder joints that could be easily fixed and also had one pack die on me randomly but given that they are less than half the cost of an enerland pack, I will take that risk. With that said, Hobbycity does sell the polyquest packs pretty cheap too. However, the value of the zippy relative to the performance can't be beat.

By the way, the Zippy-H 5s 4000 pack is really a 4350 pack. i have noticed some of their < than 5000 mah packs charge up a lot higher than their rated spec.