Shit I never realised how useful the Google calendar app is, I can just start typing the name of a customer I need to visit and it will automatically find it and add a map to the appointment with directions. Adding attachments is a game changer for me too, it's just a shame there's no way of adding attachments from a windows machine and have it sync with the Google calendar. (Without using the crappy webpage)
It'd be really cool if Google developed an app for windows 10 that's on par with the android app.
Alternatively, are there any windows calendar apps that will sync my Google account and let me add attachments?