I have one of those - I believe you're referring to "the Komfort Collar" (Magellans sells them). I have the inflatable version (no way I would lug the non-inflatable version around Europe).
Overall, I found it to be better than any other inflatable travel pillow I had used previously, but still not perfect.
I am an incredibly light sleeper, always have extreme difficulty sleeping in anything that moves, and despite my best efforts (and complete exhaustion from being away for 2 days before flying), I rarely can nod off to sleep on any flight. The problem is always the head nodding forward (even when the seat is "fully reclined", which in coach is not very reclined).
This 'round the head' collar pillow did pretty much stop the head-nod problem. But I wouldn't say it's a perfect solution: I used it on the flight over to Europe, and was able to catch short, fitful naps once in a while. On the return flight, not so much (maybe I was dreading coming home and returning to the pile of work that was waiting for me). Still, that's better luck than I've had with any other inflatable pillow configuration.
In any case, I would say that it is the best of the several different inflatable pillow-things that I've tried (including the official Rick inflatable pillow, which was a big disappointment), but still only partly effective.
They sure do look silly, though. That doesn't bother me much - there are always much weirder-looking people on every flight.
Hope that helps.