We recently did a performance evaluation comparing Hypertable with HBase. I thought users of this list might find the results interesting. The test report can be found through the following link:
Hypertable runs well on top of KFS and the latest binary packages include a KFS 0.5 broker. The Hypertable Manual
describes how to install and setup Hypertable and Up and Running with KFS
has more information about running Hypertable on top of KFS.