It works quite well. There is a lack of precision trying to drag the cursor around on Android, which is made worse on the <$100 quality devices. Using vim's keyboard commands, I can precisely edit text far easier than anything else I have used on a phone. I never used emacs because I'm not a fan of chords, and this is amplified on the phone. However, people who swipe text may like emacs chords over vim's commands and modes.