What is the issue with fewer face buttons? This is a clear advantage of the controller. On a traditional controller, I'll use the Xbox 360 controller in my example, actions such as jumping, melee attack, reloading, grenade throw, use key, deploy equipment, etc. all require you to let go of the right analog stick to perform unless it is mapped to LB or RB. LT and RT are typically already used for firing, aiming down sights, etc. This leaves you with only two buttons. On PC at least you have the option to map your own binds depending on the game, but on console at best you'll have a number of presets to choose from. Lets say you need to jump, turn around mid-jump and melee someone. What about crouch-jumping, or crouching in general? Accurately throwing a grenade mid-jump? Switching weapons, using abilities, reloading, etc?
I could go on, but the general idea is that many actions require you to let go of the right analog stick to use. Many of which if you could maintain control of the stick would allow more sophisticated "maneuvers" or better control of the game/character overall. I think this point by Valve by prioritizing more options without having to lose control of the "camera" is a smart design decision.
* I used a FPS in my example to relate to a common first-person scenario, other genres may have different use cases.
As for my opinion of the controller, I doubt it'll change my preference of using keyboard and mouse but if the claims to precision are true it would be a much more appealing secondary option. I'll stay optimistic.
