The only thing I'd quibble with is the recommendation of [[ ... ]] over [ ... ], because shell programmers used to [ will be surprised that [[ "foo" == "f*" ]] does pattern matching. But that is more or less an arbitrary style preference.

One thing I'm curious about is whether Google machines have followed Debian etc. in making /bin/sh a faster non-bash shell, or if /bin/sh is bash.