A small but very much helpful update was announced for the Google Calendar app today: sync of notification dismissals across multiple devices. And yes, this is a staged rollout, so you will have to wait patiently for the updated app to actually become available. Hopefully it won't take long.
That's really the only change, aside from the standard bug fixes. This new cross-device sync will not dismiss notifications for skinned calendar apps on devices like the Galaxy S4 or HTC One, of course, so you may just want to disable notifications for such apps and use Google Calendar exclusively at this point, because this is too convenient a feature to pass up.