My pre-order arrived yesterday with a Steam Link in tow. I've not tried controller and link together properly yet but I did have a couple of hours playing about with the controller. First in L4D2 (absolutely unplayable with the standard Valve defined sensitivities IMO, not sure why this was), Portal 2 (much better, and like others have said, I could really sense the potential for it here), and Total War: Rome 2.
Playing strategy games away from a desk KB & Mouse set up was my primary interest in getting a Steam Controller on day 1, I've always loved RTS games but working a full time desk job makes playing them in the evenings a sometimes painful business, so being able to relax on the sofa and play them would be an absolutely slam dunk win for this thing (and the Link) in my view.
Pleasingly, I can still see the potential of the controller for this purpose. I managed to win an (admittedly very easy) game of Rome 2 using the controller throughout. I chose one of the already user generated profiles for it at random and persevered. It was a chore but over 30mins of gameplay it did get easier as you might reasonably hope it would. I think within a month there will be some really well thought through profiles for every game on Steam and some common genre tropes will probably manifest themselves as well for ease between different games and styles of game.
I've yet to delve into the advance touch-pad calibration settings myself but I think this is where most of the set-up time is going to be for me, getting that movement to feel 1:1 rather than crazy jerky (L4D2) or slow, that's where the work is going to be.
In terms of the hardware, my initial impression was good, it's weight is more than you'd expect but I don't think it will be overly fatiguing. The ergonomics though, depending on your hand size, might well make for a different story and I've yet to play a long single game session with it, so...
The initial impression of solidity did fall away when removing the back to put in the supplied (Duracel, nice!) batteries. The plastic catch for this feels really cheap, as does the plastic-not-so-fantastic paddles that act as a battery cover. There is an air gap here too, so I think dust/grime build up and easy-water damage are quite distinct possibilities.
One thing that has really vexed me so far is the so-called haptic feedback from the track pads. When I first read about this inclusion from the earliest previews I was hugely optimistic and positive about what that could mean for a trackpad based controller. However, the haptic feedback I've experienced is so weak and vague. There is no sense what so ever of the haptic sensation being, for want of a better articulated wish; under your thumb. So it just feels like really weak standard pad rumble constantly. Also, for some reason it gives a single rumble like 'knock' whenever I reach the furthest degree point of the analogue stick, or to put it another way; it gives a little slug of vibration if you push the stick all the way in any direction. I found this really, really off putting and can't understand its purpose at all. To the point I'm slightly worried I've got a faulty pad. Anyone got any other feedback or opinions on that?
To sum it up, I'm really looking forward to putting more time into it to make a final opinion.
