Locally a few guys use them. I have both the Cane Creek (and totally forgot the name of them so thanks for putting it in your title) and the Scott Rakes.
I used the Rakes extensively when I was "strong" (a relative term - strong for a middling Cat 3). I was experimenting with different aero type things - wheels, bars, positions. I'd already adapted to using a TriSpoke (HED3 now) all the time up front, and a disk or a matching TriSpoke in the rear. I tried and discarded the... Drop Ins (?), the drop bars with the bend in drops. I tried and discarded the bar that connected the drops just below the brake levers. I tried and kept, for a while, the 100k Scott bars (supe narrow TT bars.
I found that if I tilted the Rakes forward a bit, they were far enough away that my knees and elbows didn't try and merge on every pedal stroke. I had them close enough together that my knuckles hit when I held the bars, and I could wipe my front tire simply by extending my thumb out from the drops of the Rakes.
I could corner, at or near the front of a tight crit, on the Rakes at maximum speed - 35+ mph. I admit I scared myself a few times but there's nothing like commitment when you're on Rakes
I've ridden fields (Cat 3) off my wheel by putting it in a 54x12 and going like crazy for a few miles. Didn't accomplish anything but man it was fun.
They're a pain to set up because your cables get in the way, sort of like clip on TT bars on a normal road bike.
Having since learned that objects at a 30 degree angle to the wind present the most drag, I think these bars are not ideal as your arm ends up at about a 30 degree angle. I'd prefer the Spinaccis (or the 3ttt version which I have but forget the name of) because they're more like real aero bars as your arms sit on top of the tops.
When I saw the Cane Creek ones, I decided to try them out but mounted differently. I found that using the "drop" bit was really awkward. No curve, straight edge, too flared, etc. My hands just slid down. I did like the light weight (Scotts are tanks, made with real thick cheap aluminum) and the more positive clamp. I mounted them so the tops are horizontal, i.e. I hold the tops like mini aero bars. It hurts my forearms (the clamp digs in) so ideally I'd put some tape around the clamp or something. I never experimented too much with them and I never trained enough to actually use them.
I took the Rakes off for races where I think I'll either be in the hunt - the weight affected me when sprinting, at least psychologically. I'd keep them on if I thought I'd get dropped (road races) or if I was going to work for the team (the same road races as the first point) as well as races where I thought that the field would be single file a lot (really fast crits, usually flat). I haven't had them on in a race in a few years, and I last had them on the bike on the trainer two winters ago.
They take some getting used to (Rakes or Speedbars in the low position) since you're really, really low. You need to work on strengthening your back a bit. Also your pedaling changes a bit so need to work on that too. You get a little more power but I never quantified that.
Generally speaking I suck when it comes to solo or extended efforts so for me the bars are more a curiosity than useful. For the TT gods I think they offer potentially significant aero advantages. I'm surprised more strong Cat 2s don't use them. I think they're worth 1-2 mph and if someone gets away...
not good enough to use'em but I got'em,