I just find it unfair criticism because hg has just as many UI kinks or just lack of UI to begin with. `hg diff` or how it's randomly split into different commands with a `-p` flag is just one example.
I don't understand why many git apologists continue to try to paper over the atrocious CLI that comes with git by blaming the user for not knowing his tools well enough. The tool is supposed to serve the user, not the other way around. Personally I think everything about the git CLI sucks, plain and simple. The command structure and naming, the switches, the error messages, the documentation, all of it. Compared to git, the hg CLI is a thing of beauty. Yet I still prefer git over Hg. No need to sugarcoat it and pretend git is flawless though.
This is a bold claim, and depends on a lot of variables. On very large repos, git is completely unusable.