Since this is on sale these days, and i've been using it since release, i thought i could add my 2cents:
If you buy it and expect to work right out of the box, like a xbox gamepad, you will be very disappointed. It has a steep learning curve, due to the dozens of available software settings for everything imaginable. The best configs are the ones you make yourself. Don't rely on the community ones, most of the popular ones are trash (valve said they working on an update, similar to steam workshop, for the way community configs are sorted and ranked).
Be careful reading older reviews/impressions, because the software got many new features and fixes since release.
Ergonomy is fine for me, i have small, average hands, it feels comfortable, with the exception of the bumpers, which are too high and hard to press (same for the L3 button). Others don't like the ergonomy, since it sits different in your hands than a regular gamepad.
The precision is there, but it requires lots of tweaking, per game. You better like tweaking and customizing... The only games where i wouldn't use it is for fighting games and for competitive gaming, where mouse is still king. Otherwise, you can make every game work with it, as long as it has steam overlay support. FPS games work better than on any gamepad, a popular setup is to use gyro for precise aiming and the right touchpad for broader moves. There's no perfect and definitive setup, it's all about personal preferences and adjustment.
tl:dr: i like it, it allows me to play all my m&k games on a big TV, sitting comfortably. I only use my m&k desk setup for Dota 2 and some competitive multiplayer FPSs. That said, i don't recommend it for people who are satisfied with their current setup (m&k and regular xbox pad) or for ones who don't have the patience for learning and customizing dozens of options and then practicing for hours. That said, it's a niche product that i'm personally very glad it exists.
even shorter tl:dr: Microsoft and Sony would never release a console with such a gamepad, not because it's bad, but because it's very different from a traditional controller, in a not very user friendly way.
