Every time I wish to upgrade from an earlier version (which is running very well indeed - with some known limitations), I wait. I see a new release, and wait. And then a bug such as this one comes up and I'm kinda glad I waited. You would think that the "engine" that is the calendar (for example) doesn't change much, so that new bugs such as these don't happen.
With the SM version I'm on with one of my clients, events don't get deleted, but some events disappear right after creating them, which is disconcerting, but then they are there, and they stay. I still haven't figured out that issue, but I'm certainly concerned about this latest wrinkle.