[leephillips]

"Vim is pretty dumb about utf-8."

It might not work the way you prefer using your favorite input method, but vim allows you to enter any utf-8 character, and even has mnemonic digraphs for many you are most likely to want. To get è, for example, in input mode just type <ctl>-k`e.

[graywh]

Using the digraph will get around the insert-mode alt-key maps.

[emillon]

or `, delete, e if digraphs are activated (IIRC)