@inof8or: The special thing about the Chris PPA is that it contains nodejs code that works with Spark CLI. Also it is the only version of nodejs with the NSA callback. [OK, for the avoidance of doubt, that's a joke - the standard version also contains the NSA callback.]
The standard Ubuntu modejs package did not work with Spark-CLI. They installed, but did not work. I also tried linking node to nodejs. I tried hard to make them work, but they did not. The version available back then (and now, I just checked) from the std repos was 0.6. This version is known to be flaky. The Chris repo version of nodejs is 0.10 - the version also available in Ubuntu 14.04 and, we are led to believe, in Debian.
@sej7278: I too am concerned about adding random PPA's to my repo list. I did a Google search. Several people were recommending the Chris PPA for a working nodejs in general - not Spark CLI specifically.
I refuse to add "you do this at your own risk" disclaimers every rare time I give a little useful (or useless) (or outright dangerous) piece of advice. In my world the grass is always assumed slippery when wet - no need for the park keeper to put out the warning signs. But you are correct to be wary.
Please, if anyone has found that the standard install of Ubuntu 12.04 nodejs (i.e. 0.6) actually works with Spark CLI just say!