Li-Poly packs require a special charger. Trying to do otherwise will cause them to explode or burst into flame. They are not dangerous if you are cautious in their use and care. The only problems I've had with them have been caused by my own errors.

Some chargers have a Li-Poly setting, but they will usually only charge at low rates, requiring much more time to obtain a full charge. Over voltaging or over current can and probably will cause explosion and fire.

Li-Poly must be charged at a no higher than a 1C rate. That is a 1200 MAH Li-Poly pack is charged at 1.2 Amps or lower. This is one disadvantage of Li-Poly batteries, they normally take a full hour to recharge after use. But they hold their charge for up to 6 months. So with multiple packs for a plane, you can charge at home, and be able to fly the batteries without peaking them first.

I suggest that you get an Astro Flight Li-Poly charger. They cost in the range of 130 dollars, but allow you to charge up to 9000 MAH Packs. This is a big advantage when you are charging different packs. I have packs ranging from 640 MAH to 6400 MAH and the charger covers the entire range for me.