It also change my life when dealing money with people. Everyone can transfer money to each other, and people assume that everyone has it (what is 95% true in my social circle). I don't need to have cash, credit card, and don't have to deal with change/money issues anymore with them. You do not need to see people physically, or ask any bank information.
There is also pretty fun to I see in many group I am in (from 2 to 500 people). You can send "Red envelopes". You set the amount of it, to how many winner you want, and if the ammount is random across people winning or not). The others don't know the amount of money in it. The X first(s) to open the red envelope get the money. I believe this increase the stickiness of the group you're in. I know some group sending many red envelops a day (for any kind of reasons). I also believe the number of red envelops sent increased a lot during the Chinese new year (It's a tradition to give red envelope during CNY).
For the fee: After 20k RMB , you'll have to pay a 0.1% fee on on every transfer. The limit is reset every month. You can also put back the money in your bank. The limit is 1K rmb/week, if that exceeded, you pay some fee (can't remember how much).