I know they released apps in Mexico and Russia... but not yet for the US.. I use SBUX and it does everything I want it to do. I pay using this app just like I did when I used the official app on my old iPhone
The only problem i have with the SBUX app is me card number was generated when I created my online rewards account. It does not have this 4 digit code that SBUX requests in order to check your card balance.
Unfortunately, we are unable to confirm if we will have a mobile application for Windows in the future, but we are looking into a solution for it. However, we currently do not have a timeframe and can not confirm if we will have the Windows app in the future.
On the plus side though when I replied and said they really ought to considering market share etc etc they sent me two free drinks vouchers!