Depending on the browser, the promise version of the CAPI sometimes fills the console with the following confusing message:

[Q] Unhandled rejection reasons (should be empty):(no stack)

It seems lilke this happens in Firefox and IE but not in Chrome (under Windows 7 at least)

Steps to reproduce: https://gist.github.com/wiseman17/7369604

(For the record, this issue is mentioned in http://stackoverflow.com/a/18112535/125264)