We have four stacks of Nutanix gear in our Europe offices. We're in the process of replacing them with generic Dell hosts and NAS storage.
When it works it's fine, but for two major issues:
a) Updating firmware usually results in bricked hardware and Fed-ex'd replacement parts to get it back up. I've had to replace six SATADOMs that failed during firmware updates. Was under support and no cost to us, but major inconvenience and left us without any backup host resources when down for days. A second host failure at that time would have been disastrous.
b) Their "CVM" is a VM that runs on each host to manage everything in addition to ESXi. This consumes 25% of each hosts RAM and is a royal pain in the keister as a resource drain. It limits your options in a small office environment.
Their tech support is excellent and their guys know what they are doing when things go wrong. However, the stuff that went wrong was caused by their updates. The additional overhead to run Nutanix is better used for our VM's on native ESXi.