I've been using my Vector 3 pedals for about a month. The training data is awesome and helps me hone in on my weaknesses.
After my first ride in wet conditions, the right pedal dropped out, it's easy to pull the battery and slightly pull the inside contact up so it makes a better connection. Power is the best way to train and track your performance improvement. Conditions and equipment can vary so much so power just makes more sense.
The ease of installation and ability to move pedals between bikes is very convenient.
Combined with the Garmin 1030, these provide a lot of useful information. They install like any other pedal - super easy. So it's pretty simple to move between bikes if necessary. I've had them for a month or so, and so far, I'm pretty impressed.
This is my first power measurement device and I've been very impressed with how easy it is to use. I connected it to my Garmin and it has worked flawlessly for the past year. I find it particularly useful for long hard rides to optimize my pace without burning myself out.
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.