I'd love some feedback on these too. I bought an early Airmotiv sub but had to send it back due to the (now resolved) hum issue. I ended up with a BasX S12, but am itching to add another sub to my main system and I'm hoping the S15 might be it.
I purchased two Airmotiv S10s back in Nov 2018. I contemplated purchasing S15s, but decided they were just a little too big if I had to move them around the room to alleviate a standing wave issue. I have seen complaints about the finish not being fancy, but mine, for the most part, are out of sight, the grill of one is visible. The S10s are solid performers and fit my room very nicely. If you have the room to put an S15, go for it. My only complaint is that they are cheaper now then when I purchased mine.
Emotiva RMC-1 7.2.4 Emotiva XPA-DR1 X 2 Emotiva XPA-Thirteen 1-6S Emotiva S10 sub X 2 Emotiva XPS-1 Preamp Rega Planar 3 TT Bluesound Node 2i DAC QNAP TVS-672XT NAS, M.2 SSD for Roon Core/library Carver Amazing Loudspeakers Platinum Edition, 60" ribbons KnuKonceptz Karma SS 8 gauge speaker wire Def Tech DI8Rs - Atmos X 4 Def Tech AW 6500s - Surrounds X 4 Def Tech ProCenter2000 - Center Klipsch-Patio BIC Venturi-Garage Carver disc changer Roku