X Air XR18 : Great

I use this to connect a bunch of synths to headphones/monitors/PC, and as a midi interface, and it works like a charm. The software for PC is relatively easy to set up and use (routing, combine stereo channels, etc) and after half an hour I was multi-track recording in Reaper. The configurations you make are saved on the device, so I rarely open the mixers config software. The sound quality is great with a low noise floor (with balanced TRS). I do not use the wifi so i cannot speak of its capabilities.

Only slight minus is that while the software works like it should, it does take some time to get your head around how to use it. Not because the software is bad, but the mixer has a lot of features and works slightly different from a classic analog mixer. For me it was not a huge deal, but for people who are easily frustrated by software it may be worth noting.