I think the cells are good, especially some of the smaller cells, but the pack construction pretty much sucks. The 3500's I have are incredible, and stomp the crap out of any gp3300 packs I've had for punch and runtime. After building them into sxs packs, I no longer had the shrink wrap melting heat problems that they had before. I've had 4 3500 packs, 2 3800 packs, and 2 4200's. I honestly found the 3500's to be the best cells.