I found Zookeeper to be pretty easy to learn about and deploy. I also found it got a semi-bad reputation with others because they did not want to learn anything. Two major examples being:

* attempting thousands (tens of thousands?) of simultaneous writes across data centres/continents at the same instant and then saying it was slow. Subscribing all clients to updates on all parts of the tree. The architecture had been grown by people who didn't understand the guarantees and constraints.

* calling it unreliable after arbitrarily moving nodes around without changing connect strings and generally mis-configuring it. Essentially, pointing clients at machines that no longer contained nodes and blaming ZK for this not working.

It could be easier to setup. People often don't want to think about such things at all. But it's also not the hardest, and I found it to be very resilient to node and network failures when deployed correctly.