Couldn't agree more. We had more problems with sharding over the years than you could imagine...the distributed locking mechanism didn't work a lot of the time

Couldn't agree more. We had more problems with sharding over the years than you could imagine...the distributed locking mechanism didn't work a lot of the time, the balancer didn't work, weird consistency issues between the config servers, configuration that didn't get replicated across all shards, stupid shard key selection (admittedly our fault but there really should be better guidance on this topic), etc.