I keep seeing the ads for those, but I don't really trust my eyes to a HF hood. I'll keep saving and get a "good" one.....until then, I'll keep using my antiquated non-auto-darkening one.
I've got one that I've had for about 1-1/2 years - seems to work just fine. My corneas don't feel burnt, and I seem to be able to see still. I wouldn't hesitate to get one - much easier to weld with.
I've used them for four well over four years with no problems to the eyes. You know when you get burnt from some small piece that lands in the one hole in your pants and goes down into your boot and you start throwing all your gear off; well to see that cheaper helmet go flying rather your $200 $300 helmet is a lot better feeling. And you don't mind letting your buddies borrow those than your nice hood you keep under lock&key!
I think they are really hit and miss...the two I have used both sucked big time. When they would actually work they were VERY sensitive to the angle you were welding at, get just a little out of position and they would turn off in the middle of the weld...I'll never trust one again even if it were free (let alone having to pay $50 for it). I'll stick with my old fashioned flip down Jackson Big window till I decide its worth it to spend the bucks on a nice auto darkening...