I spent about 15-30 minutes with the controller last night, here's my initial thoughts:
+ Weight is good (once you add batteries, if feels too light beforehand)
+ It plays a cute sound when you turn it on and off
+ The haptics are really nice, quite convincing effects such as a track ball "spinning" effect
+ Ergonomics seem quite good
- Not a fan of the glossy plastic
- The face buttons are
tiny, and seem way too far in, I keep hitting the wrong ones (e.g. B instead of A)
- The force to click the trackpads seems a bit high - perhaps will wear in after a while
- It initially feels small, but the joystick and face buttons seem too far in, and so the end result is that it feels too big for my (not that large) hands
- Firmware updates for a controller
I tried The Witcher 3 first up (non-Steam game for me) and had a ton of trouble finding a suitable configuration. The camera was either way too sensitive or not sensitive enough, and things seemed to go all over the place, and I felt I had no decent control over anything. None of the preset options felt and good and there were no community ones because it's not in Steam. There might be a way to find them but I didn't spend much time looking.
Next up I tried Fallout 4, and the default configuration felt a lot better. I was able to hold myself well enough in a firefight, even though the camera trackpad varied between wildly sensitive and not sensitive enough. The d-pad felt pretty rubbish for selecting things, but I think I'd prefer to enable touch mode for it rather than pressing down on the track pad itself.
Ultimately I think most of these issues are unfamiliarity with the controller so I don't think I can form an opinion about it yet (although the initial impression is that it's a bit frustrating to use, I will stick with it for a while). I'm not really sure of the best way to position my thumbs on the track pad and joystick, so at the moment it doesn't feel that comfortable and is a bit fatiguing.
Oh, this is really useful! I'm going to set this up, thanks.