Today, I've changed the database of my toy project, a URL shortener service, from the MySQL to the Apache HBase. It seems run well with my Java real-time web application.
Actually, it's not my first time. I was contributed a HQL (HBase Query Language) long long time ago. If they didn't tackle me, I could made something like Pig or Hive. Haha, anyways.
My HBase cluster size is 5 nodes. There's no big data yet but, it is now used for some twitter clients and a number of web sites and the rows are increasing as almost 30 per second.
Later, I'll use them for my some research work e.g., information-flow analysis, user propensity analysis, web structure mining, trend mining with the Apache Hama. :-)