Personally : I don't really care about any of those features, what I'd need to use this service everiday is simply a more polished UX (unnecessary no-timeout notifications, the kg-lb thing, etc).
Excellent, these notifications are starting to annoy me as well and a few people have mentioned the kg-lb thing so I'm definitely going to prioritize that.
I think a sensible approach would be to set an account default but still provide the button to allow data input in whatever unit. Or is the button then totally unnecessary? What do you think?
I personally think button is unnecessary. The most people will decide if they want to use lbs or kgs just once in the beginning (maybe it would be ok to create view for choosing right after registration) and this decision is based on metric system which is used in their region. If they want to change it at some point, it'd be still possible to do so in their profile settings.
