In every serious development the db architecture gets selected on the use cases specific to the business, so without describing which use cases HyperDex addresses there will be no real interest for it, name it 2.0 or "on steroids".
Record insertion affects all replicas of the data, so latency increases with replication.
The first graph on the performance page (http://hyperdex.org/performance/) shows that a 100% insertion workload will exhibit higher latency (and thus lower throughput for a fixed number of synchronous clients). Write-mostly workloads are slower, but I wouldn't say "extremely slow."