Disclaimer: I work at Joyent and helped build Manta. :)
Parallel is apparently also able to distribute a command over several hosts using SSH, although I've not tried that one.
It's like talking about bwr nuclear reactors. On the one hand, it's just a big glorified pot of boiling water. What's so hard about that?! The complexity isn't boiling the water, it's temperature regulation and redundant failsafes that prevent an explosion of radioactive materials that makes it harder to implement than a kettle of hot water for brewing tea.
Sure you have Cloudera et al., but I'm still trying to figure out if they really make things easier or worse when it two weeks later comes to figuring out why something is broken, or how to start/install additional Hadoop components.