"Follows the bigtable model, so it's more complicated than it needs to be. (300+kloc vs 50 for Cassandra; many more components). This means it's that much harder for me to troubleshoot. HBase is more bug-free than Cassandra but not so bug-free that troubleshooting would not be required."

I only had problems (data losses) when I was using HBase in production 3 months ago, but I'm certain that HBase will be mcuh more stable in a few months. And there comes that Cassandra developer and says that Cassandra even has more bugs. Lol. Now I'm pretty sure that I will never touch Cassandra as well.