I have had 3 Fitbit's now (took each one back as they started to fall apart within the warranty period). The last two had HRM's. My primary purpose was not to monitor HR but the other stats (steps, floors etc), HR monitoring was a nice to have an of secondary importance to me. I also found it to be less than accurate in measuring HR. For example, I would do High intensity interval training on my exercise bike and record my HR the old fashioned way with two fingers on the carotid artery. The manual way gave me a reading of 160-170 bpm, however the Fitbit would read 125!
I have just purchased an Apple watch and am looking forward to getting some stats out of it (have only been wearing it a few days). Although I'm finding it a bit more challenging navigating the Apple watch and related apps than the Fitbit.