Valve's haptic-feedback-based Steam Controller has been delayed until next year, Valve has revealed.
The experimental controller is currently in the midst of playtesting and Valve's Eric Hope stated on the Steam Universe community page that "It's generating a ton of useful feedback, and it means we'll be able to make the controller a lot better. Of course, it's also keeping us pretty busy making all those improvements. Realistically, we're now looking at a release window of 2015, not 2014."
"Obviously we're just as eager as you are to get a Steam Machine in your hands," he continued. "But our number one priority is making sure that when you do, you'll be getting the best gaming experience possible. We hope you'll be patient with us while we get there."
This suggests that Steam Machines won't be commercially available until next year. We've contacted Valve to confirm this and are awaiting a response. We'll update as we hear back.