The Meizu MX4 has a BT40 inside. I have checked online and it is relatively easy to replace it yourself. The original battery is made by Sony. On eBay there are many OEM batteries, not made by Sony, for very attractive prices. Are they any good? How are they compared to Sony? Should I pay more for the original Sony?

Would like also to know if anyone replaced the battery himself and how easy or complicated it is?