I heard that it heats up the phone and it ends up ruining the battery.

http://www.qiwireless.com/is-samsungs-new-wireless-charging-pad-worth-the-price/

"It's (mostly) wireless, but it ain't fast. It takes just about two hours to fully charge my dead GS6 edge using the charger that ships with the device, which uses Samsung's "Adaptive Fast Charging." It takes just under three hours to fully charge the dead device using the wireless charging pad.

It can actually drain power if used improperly. If you don't place your device firmly in the center of the round charging pad, it can get stuck in a loop of connects and disconnects, which rapidly drains your battery instead of charging it. This is easy to avoid — you just make sure your phone is properly placed on the pad. However, if you're in a rush, drop your phone on the pad and then leave the room, you may be disappointed to find a dead device. (I know I was.)

Wireless charging equals warm phone. If you charge your device for any extended period of time, it's going to get rather toasty atop the Samsung Wireless Charging Pad. It's doesn't get hot, but you'll notice the heat when you first pick it up off the pad. It's not uncommon for batteries to emit heat while charging, but the effect seems to be more noticeable when I charge wirelessly compared to a traditional, wired charge.

It's slightly pricey. Samsung charges $50 for its new Wireless Charging Pad, which isn't expensive, but it's also not cheap.

You need to use appropriate cable. Samsung says you can damage the charging pad if you don't use the appropriate cable to charge, so don't plan to use any spare cables you have around the office."