Yep, I have a mixed relationship with the powertap. At one stage I was convinced it was under-reading, so I sent it for a service and it came back reading exactly the same... 😭
I like the powertap though, for me, it's a better training tool than heart rate. I will admit that the hub is quite heavy though - adds about 300-400 grams on a normal hub.
RE: Today's ride had no legs