As with Acompli, Sunrise looks nice and has some nice features, but I can't get over the privacy/security problems. I'm interested to see how Microsoft can improve things.
It's a calendar app. This stuff already syncs like crazy as it is. I would never consider a calendar secure, and would never put confidential information in it.
Think of, for example, medical offices: patient names are PHI. Assuming Microsoft does with Sunrise that it did with Acompli, I could easily see a small medical office thinking, "hey, this calendar is really cool and it's from Microsoft, so it's okay to use".
Should they have read the FAQ and seen that it's not HIPAA compliant? Of course. I can also see easily how Microsoft's reputation in business could lead to the assumption that their new acquisitions are business-grade, in spite of their consumer origins.
To bring it around to my original point, I'm interested to see how Microsoft can improve these apps to the point where they meet the expectations for Microsoft's business products.