Yes is still not perfect..because on my mi2s works only for YouTube links in Firefox..but Doesn't work with tapatalk, google play... links.
C'mon Xiaomi, i think this feature has most priority than others
In settings-applications you can now select default app I. E. Default browser..and works.
I had this problem in lasts releases but now is perfect.
When I open a YouTube link Firefox ask me if I want open with yt app
Thank you Xiaomi