Martijn
Haven't used it. Glanced over the website and the fact that I can't read about what encryption they are using (other than it being 'end-to-end') really irks me. Them writing Peerio is 'professionally audited' without linking to any such audit doesn't strengthen their impression on me. The website seems to have been build for marketing more so than informing their users.
John Olinda
Yeah, I am fooling around with it, just not for anything sensitive obviously. I know his intention is for it to be very simple to use, but I would have liked to see the audit reports too. Wired did a big writeup on it and mentioned the audit too.