UPDATE April 23rd 2014 - GOOD NEWS!
The final production Primo 8 arrived today, and with the included Nuforce silicone tips they clearly sound better - I was really excited to hear them.
Jason tells me that they switched from a softer PVC plastic that was used in the pre-production to a harder polycarbonate shell, which appears to have improved the sound. I think the Nuforce tips may contribute to this as well, as they are also better sounding than the Complys T100 that came with my pre-production and production Primo 8. The bore of the silicone tip is larger, and more perfectly matches the bore of the IEM. It's like the difference between the old Westone silicone tips and the newer "star" tips, but instead of impacting the treble only this also impacts the bass, no pun intended.
The biggest improvement are (1) increased bass, and (2) the ability to perform much better with my iPhone 5s and NO amp! This is going to instantly appeal to a larger number of people than just audiophiles.
(1) The bass is noticeably improved in quantity, and it seems louder by at least a full 2-3 dB in the lowest regions vs the pre-production pair (regardless of Complys or Westone silicone tips on the old pair). I don't hear any negatives in quality to go with the increased bass quantity - it's still fast, tight, and textured, without bleeding into the midrange. This is a natural sounding increase, and what I was looking for with all the versions that were improved during the beta testing. Wow.
This improves the weight and body of instruments and vocals, without making them sound too thick. And Diana Krall sounds just as sexy as before, without her already husky voice getting any unnecessary enhancements.
(2) I can also enjoy the Primo 8 more with my iPhone volume turned down to 50-55%, rather than going up to 60-75% to get better impact with instruments. Something like Christina Aguilera "Can't Hold Us Down" is a real pleasure now directly out of the iPhone, without to crank it up louder, or mess with an amp and it's output impedance settings or bass boost switches!
(3) The other GOOD - the included in-line microphone sounded good to my wife when she called me while I was listening to music today. She was in her car on her bluetooth speaker, and she said that I sounded clear and easy to understand. The button works fine, and I can answer calls, pause music, and skip forward or backwards with no problems. The button is large and easy to find at the Y-split without looking and doesn't get easily pushed by accident. At first it was so large that I thought the button was a 3-button switch not a 1-button, but I was wrong.
(4) The BAD, is that if you like to wear the cable over your ears and behind your head like a musician on stage, then it puts the microphone behind your back instead of being next to your neck and under the ear as with other IEM with an in-line mic in the cable.