Picked these up.
They do work very well under a helmet, with pretty much nothing sticking out at all if you position the cords to hang under the ear and turn them so that they are tight against your lobe. The control module hangs just under the helmet, barely clearing it (Shark Evoline 3, Large) and can be positioned so it shouldn't whip in the wind. They can be set up so the module is on either right or left, with left being the obvious riding option so a hand can be free.
Sound is excellent with a good seal. It held a BT connection well, I didn't hear obvious hiss at reasonably high levels, and the default bass and sound was good enough I don't feel the need to EQ them yet, after listening to EDM, hip-hop, rock, metal, and a few other miscellaneous things. They're at least as good as my Klipsch S5i Ruggeds, and don't seem like a step down from my MA750s--with a good seal.
Getting that good seal, though, is kind of a pain. This is obviously very subjective, but they include three silicone sizes and three sizes of Comply Sport foamies. I normally use double-flanged and those aren't included, though I'm sure I'll find some flanged tips that fit after a bit of research.
The foamies were really disappointing. I have Comply foamies for my other headphones, and they work well. But these don't appear to have much (if any) memory foam going on. The mediums felt like standard open cell foam--they didn't hold a squish and seemingly wanted to be shoved straight into my ears. Maybe wetting them would work, but I wasn't able to get a seal whatsoever that way. I didn't try the small. The large did squish but not very much--they were like low-profile tires in terms of the foam to middle ratio, and didn't feel like they expanded into my ears like the other Complys.
Maybe this is the sport foam? Not sure, but I thought the foam tips outright sucked, which is unusual for Comply. I'm hoping I'm either just missing a technique, or that I can get a different type of foam from Comply that'll fit and actually squish/expand like I expected.
I was able to get the medium silicone to work, but I'm kind of in between medium and large and it wasn't a very robust fit. In particular, they had a tendency to actually go too far in and form a vacuum seal against my ear canal that was both uncomfortable and muted the sound--I have tons of IEMs and it wasn't the right type of "good seal". Large sounded strangled in that "so oversized you closed the end hole" kind of way so were a non-starter.
Honestly, this is pretty similar to my Klipsch experience--oval tips turn out *not* to work for me well--and was a bit disappointing out of the box when I otherwise don't have a problem finding good seal on my other IEMs. The S5i issue was compounded by not finding good replacement tips that worked with the retaining lip on the stem (and a subsequent trip to urgent care with a Comply tip wedged in my ear). Hopefully it will work out better here given that Jaybird has become pretty popular.
I will say that they are insanely light, at least without the charging module snapped on. With it snapped on, they're still not heavy but I wouldn't want to go running without it clipped down somewhere to my collar. It's enough extra weight/size to be noticeable and to pull the cords to the side some. I suspect over-the-ear might solve this, but I wasn't able to get the cords to work well for me that way out of the box as they're thick enough to try to straighten back out, but not thick enough to just hold a shape. I'm sure they can be "trained" with some work.
One concern is that the tip of the stem is pretty close to the opening in the eartip. The stem has a handful of very small holes in a daisy configuration to let the sound out. I have waxy ears, and I'm a little unclear if wax can wedge inside the stem in a way that can't be cleaned with a hearing aid loop. I see something just inside it, which could either be A) a filter or B) wax I already got into it and I'm a little worried it might be the latter. That said, I poked at one of the holes very gently with a plastic interdental pick and didn't come back with wax so I'm hoping it's a filter.
Aside from that, haven't used them enough yet to have a clear opinion beyond the very good first impressions. I still need to check whether the BT connection tends to have a ton of latency (this is variable but I've definitely noticed some of my cans do better than others, probably a codec issue), if the connection is truly solid, battery life, etc. With some work on the tips, though, I think these are pretty cool and I'm glad I got them.