Impressive indeed. It works out in a way if you'd like to to upgrade to the latest version of HBase without involving a data migration. Am switching to the new version right away.
CentOS is a good choice if you want to run a server for commercial purposes. I use Fedora (its almost the same as centOS) for my development desktop as it mimicks my server setup. I tried Ubuntu for my server and it didn't work out to be that stable. However a couple of my friends in other startups found Ubuntu to be working fine for them on their production servers. Another distro I use a lot is Backtrack ;)