Ive been using kraken for a while.

I Use it because of the options to margin trade Btc, Eth, xrp at 5x leverage.  The information it provides regarding positions as well as having a variety of order types I think is awesome and one of the best.

It is a old school, established exchange with a excellent security record and has good liquidity.

It also allows you to trade euro/usd/yen pairs

Its fee structure is expensive, unless you have achieved a significant trading volume amount which is the only downside for me.