I think even the most skilled programmer can benefit from making their code pass -Wall completely, even if just for the sake of sharing with other developers (but we all make mistakes and it'll likely catch some of those too!).
There's a reason that for quite a number of these warnings, Go has either designed the causes out of the language (no implicit casting, only manual conversions), or promoted them to compiler errors (unused variables and imports).
I disagree (not "strongly" because your clarification in the next paragraph). That's only true if you don't know what are you doing.
That said, I am a big fan of gcc's -Wall since the late 90s, and I can tell you gcc has improved a lot since then.