I use the Compose key and iirc it used to work in text inputs before I upgraded to trunk a few days ago.
Reproducing is easy: Open any text input (like the search field on http://www.google.com ) and type a compose sequence like "[Compose] < 3"
Expected result: ❤
Actual result: <3
This seems to be working now. Probably because IME fixes from a few years ago.