Don't trust their code

Whenever I am searching for open-source software that solves some specific problem I always fetch the source code and read it in order to understand the general structure and code quality. One of the indicators I look for is the output of the following command:

$ ack -ai 'TODO|XXX|NOTE'

This will more often than not give me a pretty good overview on the completeness of the software in question, quirks to watch out for and general coding practices.