Have had a Precision 4iiii dual-sided power meter Ultegra crank for about 15 months. The difference between my left and right is typical 1%, so in the future I would get a left-side only power meter.
I have had problems in the winter with the batteries draining quickly. In temps in the high 30s, battery life has been 2 hours. Sometimes batteries have drained overnight in my basement. 4iiii said to zero set before rides. I said I do, so they had me perform a procedure to reset the power meters. After performing that procedure, the left power meter was rendered non-functional. They said to ride my next race a few days later with just the right side power meter. Well, the right side reported power for only 5 minutes of the race. Don’t know if it is non-functional. Sending the crank back to 4iiii for repairs,
Will be purchasing a power meter for another bike next month. It will be a new bike with a GRX crank. Whether I buy another 4iiii is going to depend on whether they resolve the issues with my Ultegra crank.