Use only the close button, get rid of the hide one. Notifications should be pushed to the notification area after the few seconds have expired and if the user has not closed them himself.
This way if you want to see something later, just don't click the close button. As it is, they are close enough that it would be easy to misclick and manual hiding means you are actively going out of your way to, well, not be distracted. And that is distracting.
Quite like the texture and how you organized it, looks pretty good.
1 - Don't you think that adding another button (hide me) would make it too complex? I mean, If the behavior of hide me would be (I suppose) hiding the notification to the notifications center, would the close button just vanish the notification? And if that's the intended behavior, don't you think that the decision of vanishing a notification or just hiding it in the case of an undergoing, non-finished process should be handled by the notification software itself?
2 - Why the decision of keeping calender events in the notification center? I think the date-time in the toolbar is a much more intuitive place to look for my appointments. It's how Gnome-Shell does it and it seems really practical and nifty (can't speak about it myself because I don't tend to use calendar apps so much). Maybe not its Layout, I think it uses too much space. Maybe clicking on a day with an event on the calendar would expand the indicator and show the events for that day?
Of course, those are just my opinion and that's why I'm asking you about those things. Really enjoying the looks, mainly the texture.