Interesting. I have the 235 to and mostly I like it, especially the comfy strap and the Bluetooth so I can update attackpoint from my phone. I don't really do intervals anymore so I don't have data from that but my sprint track from the weekend looked pretty plausibly above 160 the whole time. You do need to make sure the watch is tight or it really won't work. I think you can still use a heart rate strap with it if the sensor isn't working out for you. My one thing I haven't figured out is the watch seems to be taking splits for me based in heart rate, I think, so if I slow down at all or maybe just randomly, the watch buzzes and takes a split. Which is super annoying if you're stuck trying to get up some little ski-o track and your watch is buzzing every nine seconds. Is your watch doing that? I tried googling and couldn't find anything useful.
Yeah, I think I need to try tightening it more for runs. And maybe wearing it a bit higher. How far from your wrist bone do you wear it?
I generally don't use HR info when I run, unless it's a long tempo run on dirt or something, but it would nice to have the info. I got it specifically because I was tired of dealing with HRM straps, which give me funky data AND have the bonus of chafing. I suspect I will soon have something like 4 Garmin HRM straps to give away...
No problem with buzzing, I have auto-splits and auto-pause and alarms all off, I think. Is it giving you HR-based alarm buzzes? And you happen to exercise right around its threshold? ;-)
My watch is definitely clear of the wrist bone. The most knobby bit on the top outside edge is pretty much just next to the watch face.
I should look the thresholds. I thought it was just noticing that my heart rate went down but the thresholds makes more sense.