The button layout on Valve's still-prototyping Steam Controller continues to evolve, as a data file found in the latest beta version of the Steam client (found in the Steam\tenfoot\resource\images\library if you want to see for yourself) shows a new revision of the device with one major new change: an analogue thumbstick (thanks PC Gamer
During the Steam Dev Days event back in January, Valve had revealed a new prototype Steam Controller with two sets of face buttons in diamond layout, with the stated aim of making it more compatible with existing controller supporting games. However, it now looks like they've removed the left-hand side d-pad buttons and replaced them with an analogue stick, while still retaining both left and right touchpads as the primary analogue movement inputs.
The image also confirms that the lower rear grip trigger buttons are still present, in addition to the more traditional upper triggers and bumpers. There's a lot of inputs on this thing.
The Steam Controller is still expected to launch alongside third party manufactuered Steam Machines, which was originally supposed to be happening in 2014, but has been delayed into next year
while Valve gets SteamOS retail ready.