I have 2 left sided pioneer PMs and they're both flawless as far as functionality. I have an Ultegra 6800 meter on my CAAD 12 and a Dura Ace 9100 meter on my Allied Alfa. I initially bought a stages PM for the CAAD 12 and after 3 rides with extremely poor performance I returned it and bought a Pioneer. The only drawback for me is lack of Bluetooth functionality (i.e. for Zwift, etc) but I have a Kickr for power anyway.

I should add that buying a PM from competitive cyclist was awesome. Like I said I bought an Ultegra Stages left sided PM and used it on 3 rides and it was awful. Tons of dropout, erroneous power readings, just terrible. I called them and they took it back. No questions asked. Sent them back my used Stages and had a new Pioneer on my door 2 days later. They're great.

I thought Zwift can pair with both ant+ or bluetooth? The pioneer being ant+ I would have guessed it to pair even with a classic trainer. I won't be upgrading to a smart trainer anytime soon so this is a big selling point for me.

Zwift can pair via ANT+, but whatever device you're using to run Zwift needs to have ANT+ communication. Pretty much all tablets, phones,computers, and Apple TV can connect to power meters and HR straps through BT out of the box. Many of them will need an ANT+ dongle in order to work with ANT+.

Ok got it. That makes good sense. My quarq communicates with Trainer Road via ant+ and a dongle to my laptop. So pioneer and zwift would be the same.

Yes I should have clarified. I use Zwift on Apple TV so it requires Bluetooth. You could use the pioneer meters with a computer and ANT stick.

Have had one for a year on my CAAD12 disc. Has performed well over the year. No issues so far. Tracks well with my Quarq and Kickr.