I just got my 2015 15" today. I'd used Force Touch on a 13" in the Apple Store but now I'm using it at home I can give my proper thoughts after a few hours.
I quite like it. It feels like a real click to me, it doesn't feel like it goes down as far as the real moving trackpads but I'd say it feels about 50-75% as deep when clicked. That's on the "firm" setting. Feels nice.
The force touch part where you push harder to get a second click, that's really cool. Feels deeper than the first click does and works really well.
Overall I'm quite impressed. Very cool engineering. I wouldn't call myself a click purist or anything but I do like a nice tactile click to my trackpads and the force touch trackpad for me gives a nice assimilation.