If you turn on smart filters, it'll try to club promotions / payments / forums etc. smartly. It'd be right 90% time. But my threshold would be less than 1% failure.
If you open an email in Inbox, it'd recommend quick action replies like "Thanks, got it." or "Lets meet" etc.. It was on spot a lot of times, but I always wanted to add something more to the message and that's why I didn't use them.
> This is something I'd actually pay to use. Hell, long long time ago I backed a project for an Android tablet homescreen that was supposed to rearrange visible widgets depending on your location and time of day
I used One Plus2 briefly which had an area for smart apps. Since I could never predict what would be there, I never used it. I went there a few times to see if it would shorten time to action.
iOS has a recommended app at bottom left of lock screen. I use it purely as discovery. I've never found acceptable hit ratio of recommended app in my situational context and now I've blindness to that particular place.
If Knowmail guys are reading this, I'm not trying to discourage the product. I think Smartness should be in "Search mode" and not "Action mode". Action mode is when I want quick decision making and less evaluation. Search mode is when I'm open for back to back snap evaluations and unsure of next steps. i.e. don't interrupt my natural patterns. Ofcourse, I'm just one data point.