I've bought lots of batteries that came from china and were cheap knock offs of other OEM or model specific batteries from eBay. Honestly I've never had a problem with them, but I do watch them closer then an OEM battery.
For instance when it's charging for the first few times I do it with the back cover off so I can tell how hot the cell is becoming. If it gets too hot too fast, then I'd throw it away, but I've never had that happen to me.
FWIW I'm using a 1600mah battery that I got for $12 shipped from eBay and it works great! I can make it two days if needed without a charge, or through a VERY busy day with 40% left before bedtime. Not too bad for $12 in my book...........