just reading some reviews on those zippy packs, your only looking at about 30-50 cycles from them. Where as the ones I was looking at were well over 150.... so twice the price for 3x the cycles. Now again thats in RC planes which are going to have alot more constant draw.
The could be fine in airsoft guns. Just never let a lipo drop below 50% voltage I think it is, or your fucked. Well the battery is anyways.