Searching for help online results in solutions for ancient versions or incomplete wiki pages ("we'll finish this soon!" from three years ago).
If Apple is one extreme end of the user friendly spectrum, hadoop is at the polar opposite end -- the error conditions and error messages can be downright hostile. The naming conventions are wonky too: namenode and secondary namenode, but the secondary isn't a backup, it's a copy. And don't get me started on tasktracker versus jobtracker (primarily because I can never remember the difference).
Restarting a tracker doesn't make it vanish in the namenode, so you have to restart the namenode too (at least in my CDH3 setup).
Everything is held together with duct tape shell scripts.
On the good side, I got everything hadoop related managed in puppet. All I need to do for a cluster upgrade is load a new CDH repo, reboot the cluster, then make sure nothing is borked.
If I didn't have to deal with isomorphic SQL<->hadoop queries, I'd start over using http://discoproject.org/