The main thing for me about it was the fantastic UI, really slick and pleasant to use.
When Sunrise died I switched to One Calendar, which is also pretty fine. But I might try Kin anyway, and possibly switch again.
EDIT: And I think Sunrise had that rare and wonderful thing, a rolling four-week window as an alternative to the one-calendar-month view (I find it annoying near the end of the month to keep having to go to the next month's view to see a few days ahead, and have no need to see a calendar month at a time).
I use OneCalendar by BlueEdge. It syncs with google calendar, it flows nicely and can easily filter out different events.(removing class schedule or work schedule with one tap of the pen, then re-adding with another) It doesn't have "pen-notetaking" AFAIK
http://www.onecalendar.nl/#/onecalendar/overview
http://apps.microsoft.com/windows/en-us/app/onecalendar/d90f8383-6166-4a15-9235-d46feba049a2
edit: It looks like they have a feature request page on the website. (http://www.onecalendar.nl/#/windows8/featurerequests) I'd be willing to "second" pen-notetaking if anyone wants to reach out an contact them.