I have found iTerm to have very bad performance relative to Terminal.app. I honestly have no clue why its so popular, I cannot stand it.
Please try to explain your performance issues, the author is active on HN and perhaps he could comment on it.
Host * !github.com
LocalCommand printf '\e]7;file://%n/\a'
PermitLocalCommand yesSeriously, I don't understand what the benefits are, if it's only "just as fast as Terminal.app".
But among those features is tmux integration and now python extension support.