The most popular pack is probably the maxamps 5k packs, but I do have to say that the "better" packs are well worth the money. I have not yet had to opportunity to try the flightpowers, but I do have a couple of Kokam packs. Yes they were expensive, but worth every penny.

No matter how hard I run them, they never need more than a couple of seconds of balancing and when I charge them on my thunderpower 1010C, the charger tells me that there is 0.00v imbalance. The packs also have a very good punch.