I kind of wish coreutils had more standardized flags (i.e. -v will always be version, -V would always be verbose, -s would be silent or quiet so there would be no -q flag). Apart from that, the important thing is that the output is easy to parse with grep or cut, there is no extraneous debug information, errors go to stderr, and overall it just works nicely in a pipeline.

Also, I agree with jkl's point that the GNU tools have way too much extra garbage built in. `ls` (for instance), does not need a sort flag. That's what `sort` is for.