Thanks for the response! At first I thought it had improved. Yeah, I've checked, and its still spiking badly. I will say that the app smooths out some of it, but certainly not all - and all that means is that those smoothed areas are where the Band was unable to maintain a lock, so the app had to guess at it. On today's indoor cycling I had to eventually give it up and stop tracking with the Band and deleted the activity; there's just no sense in recording totally inaccurate stats. It was spiking as high as 170/180 when it should have been quite steady around 110. This was even after the initial 10 minute period, after which it usually settles down.
I think the Vivoactive HR is a good option. I have two primary reasons for choosing the Fenix 3 HR instead. The most rational reason is that the Vivoactive doesn't support power meters. The less rational is that the styling of the Fenix 3 is just so darned pretty. I already have the regular F3, so I'm quite used to it, and the Vivoactive would be sort of a downgrade.