Admittedly, my experience on this was running it on now-ancient Android devices before Dalvik had JIT, and ProGuard at the time seemed to always render Scala apps un-runnable, for whatever reason. At least for me at the time, it was questionable. Nowadays, given the amount of work put into it, I'd put some trust in running it in production. But I'd still expect issues to come up now and then, as it's not a natively supported platform.