Bitfinex allows x4 margin.
BTC.sx allows for larger margins but I don't remember how big.
BTC.sx is 1:10.
Anyone use it? Any comment about this one?
I've tried it, it works in general but there are some annoying things about it.
First it looks as if they have some kind of weird margin call system which means that you can never lose more than a specific amount on a trade, rather than just losing your entire account balance. Not sure what the point of that is. Interest is counted for this margin call system.