Having the user interface in English is not much of a problem. But voice input for the Watch app fails (in French at least) when numbers are not translated into digits by Siri, which happens with single-digit expenses that get translated into "huit euros" instead of "8€". Major showstopper! Hopefully by saying "zero huit" gets Siri to recognize "08" but we have to drop the currency or else she thinks "08 euros" instead of "08€" and the app fails again to recognize the expense ;-(
François Bourdoncle about Splitwise, v4.0.2