I have been riding with the Pioneer left side for couple of months now and it has worked perfectly. I have had zero issues with calibration, connections to my Garmin Edge 1000, or connections to my PC based ANT I use for inside training rides. So far I haven't noticed any significant differences in power readings between my bikes that have Stages PMs but I haven't really studied the data closely. The Pioneer factory warranty is 2 years vs 1 year for Stages. Round trip from Portland, OR to San Diego to get the PM installed on my left crank arm was 7 working days.
I've wanted to track my power for some time but power meters have always been prohibitively expensive. This was a great option. When I got the package, I just needed to ship out my crank arm with the packaging. Roughly a week later and got the crank arm back. So far it seems to be great with tracking power. It connected with no issues to my GPS.
Make sure you have at least 10mm clearance between the crank arm and the frame of your bike or it won't fit!
I bought this kit to retrofit a crankset I already owned, rather than shelling out for a new crankset. The sensor paired quickly with my Wahoo head unit. Relying on left-leg power data does make it somewhat hard to maintain a steady level of effort, and you might lose some accuracy if you're right-leg dominant. However, this option is fine for a basic and economical training tool...One caution my kit contained outdated shipping instructions, so UPS bounced it back to me after 2 weeks as undeliverable. Pioneer's service rep helped me resolve this, but you might want to contact Pioneer in advance to confirm their address and avoid the hassle.