So it seems as if the Seam Link and Steam Controller are not working at present. If you where a buyer who experienced this issue, it would be a unpleasant discovery.
Yet it seems as that Valve are trying to make things right to all the buyers. Not only are they promising that they will fix the issues in the coming weeks, but they are offering them all Valve games present and future as an apology gift.
According to the email Valve is sending out they want to "apologize for the delays in providing full functionality for the Mac platform. We're doing everything we can to resolve the issues. For the latest fixes and functionality, we recommend that you opt into the Steam client beta."
It is good to see Valve working to make the situation right. Hopefully they will have fixes for the release when it launches to the general public on November 10th.