Only problem with those imaps is that now you can't type ì, ë, ê, or è. Vim is pretty dumb about utf-8.
I'd also suggest using <C-o> instead of the <Esc>...i dance.
Edit: "The way [Vim] stores alt+letter in its input queue collides with UTF-8/Unicode handling" -- LeoNerd in freenode/#vim at 2013-04-15 15:22:29