I bought a used Model 1 a couple of weeks ago and use it for mixing all my synths. I find it extremely flexible, yet simple and intuitive. I send aux 1 and 2 to Analog Heat and OT AB, and use cue B as a third aux send to OT CD. AH out and OT cue go into the two return channels. The DSub connectors are very handy for connecting everything. As all channels are stereo and cannot be panned, I run my Lyra through a stereo splitter cable. There is one issue I encountered with the zero-crossing detection for switching on the master filter and master EQ: when the signal is weak, it does not react immediately. I do not know whether this is a common problem or just my mixer, and I contacted support about this. In practice, as soon as you are using multiple channels, it works well. Overall, I am very happy with it - the sound shaping possibilities added a whole new layer to my music making.
Edit: another (more cosmetic) issue I have is that the printing/lettering on the mixer surface gets rubbed off quite easily - I saw this also mentioned in one of the reviews. Shouldn’t happen at this price point, but does not affect the sound…