I got to go to GDC and check out Valve's booth and got my hands on the latest controller. IT felt pretty good to hold.
The face buttons and d-pad aren't hard to reach, but they press way too softly for my liking. I asked one of the Valve devs if they were thinking of using mechanical switches for the face buttons, and he said the last version did, and people thought the buttons felt cheap, so they put in silicon membrane switches instead. Makes me sad.
The triggers are analog, but with mechanical switches too, so it can act as analog input or digital input , or both simultaneously, on the software end. The accentuation force was at the very end of the trigger's depression so it doesn't move very far after the click. I would have liked to see the accentuation force a little further out.
Seen a lot of articles on the internet saying the touchpads felt way too twitchy and sensitivite. They definitely weren't as nice to use as a mouse, but I would say it's still a lot better than using two analog sticks.
Asked a couple other questions of the devs there:
So far no games are implementing the haptic of the touchpads to pass through information such as explosions in the way a standard controller's rumble does. I asked him about implementing that in first party games, he made it sound like they really weren't interested in doing so, but that if they decided they wanted to they would and could. It's a little dissapointing, I'm not sure why he seemed completely disinterested in implementing a feature that is considered standard in all other controllers. Perhaps they aren't using it because it'd mess with the haptic feedback used to emulate physicality, but the tone I got from him seemed to be that they just really didn't consider it a worthwhile feature.
Portal 2 has native support now as opposed to legacy support, so the left touchpad is actually implementing analog movement as opposed to emulating WASD key presses. Didn't seem very noticeable or practical in game when I tested it out. The final wireless version will be using a proprietary wireless stack and a USB dongle. The current wired version is using mini USB as opposed to Micro (bizarrely enough the dev I asked this one didn't even seem certain of she answer, so maybe it isn't mini US. All this is also very disappointing. I asked why they weren't using bluetooth, but she didn't seem to know very much and couldn't answer.
You will be able to change whether or not the controller is emulating an analog stick or a trackball from the steam overlay. This also works in legacy mode, so you could say, set the right touchpad to register as a trackball to the computer, and the left toucpad to register as a standard controller's analog stick. This way, if a game without native support steam controller supports analog input via a standard controller, you can still get analog movement out of the steam controller in legacy mode. Pretty cool.