<---- Staff Systems Engineer

As I teach junior engineers -- perfect is the enemy of good. There will always be sources of noise (uncertainty) in the system that you can't afford to design out. So you design in enough margin that you don't care. The same is true for power measurement and training. Your legs don't need extreme accuracy. For example, if your workout calls for 3 minute VO2Max intervals you need to be somewhere between 105% and 120% of FTP. Target the middle of the range and even a 10% difference between power readings on your FTP test and your current workout won't take you out of the zone.

Back in the day, riders got plenty strong training with RPE and occasional heart rate measurements with a stopwatch. Virtual power, when used wisely, is a useful tool for amateur riders. There's nothing wrong with using something better if you can afford it, but if you are talented enough to actually need it, your sponsors will hook you up.