Is anyone allready using this combo? It's such an elegant system. 

I haven't but glad you posted as I have never seen this before and it's exactly what I'm looking for, not so much as an audio interface, but for live shows. Looks like it would work with Sonar or any DAW. What I would do is record live to the USB stick and dump it to Sonar for editing. 
I was looking at the Motu Ultralite Mk3 or 4 and the Behringer X air 12. This gives me a 3rd choice in that category. 
Motu has been having Driver issues of late, and I'm forever leery of the "B" brand from past experiences.
Soundcraft appeals to my brand sensibilities. 
I picked the Soundcraft Signature series out of all I looked at in analog mixers as my first choice. But with Analog boards you only get 2x USB, 1 lousy Effect engine and never enough aux outs. Analogs only attribute is you get the control surface. I'm a little apprehensive about Tablet control. 

Be advised that the Behringer X12 only delivers stereo audio over USB. The X18 is the only one of the range that does multitrack audio over USB.

You can use ethernet with a laptop if you prefer btw.
Or if you want a minimal "on board" interface, consider the Allen & Heath Qu PAC. It's in a different price bracket but really nice and even expandable with a stage box.

I just bought a Soundcraft Signature series 12 for live use. The MTK version does multitrack over usb. I believe mine will only do 2 track or stereo out, but I have an interface already for recording.
Look forward to hearing your review.