Valve is reading this thread as we speak, I personally think this is a great idea
Wait, seriously?
Things I have concerns for/would like:
It's already been mentioned, but for racing, it would be AMAZING if there could be a "wheel mode" where spinning your fingers around the edge of the trackpad would increment a left/right analog value as you rotated. IE, it would not send that your stick was in the upper left corner, but rather slowly incrementing the left and right analog value. That way, "rotating" your dial 360 degrees would result in an analog value of 100%, but rotating it only 180* would be a value of 50% left or right. It should of course be configurable for various degrees of accuracy, but I think this could do a lot for racers.
IMO, I don't like Analog triggers, but I know a lot of people do. To me a digital trigger is far more responsive and usable. If there's a V2, I'd like it if there was some level of "stop" to get the same throw as on a digital trigger, but I understand if that's not possible or feasible.
I think I might've mentioned it before, but being able to set the controller into a "static" config that would persist through unplugging the controller and plugging it into a completely other device would go a long way in putting in some more bang for the buck, since that would open up usage on other systems (such as PS3). This would of course be saved for a later update.
They should totally get with OBsIV at XIM4.com on that last point, to see if there's anything that they could do to get the Steam controller and the XIM devices working nicely together -- that would probably get me to get a PS4, tbqh.
I would LOVE LOVE LOVE LOVE LOVE if I could get the Steam controller to use the Nintendo layout of buttons, as opposed to the Xbox one. Even if it means taking the controller apart to swap some button faces around, I would be HAPPY AS HELL. But that would require a level of software awareness, to apply those settings across everything. I know that I could just remap every game with it, but I would be happy to see some Valve acknowledgement of this preference -- I'm not the only one.
That's all I can think of right now.