I agree that the Third Eye is a bit of a disappointment, even though I paid $1 for mine at a swap meet. Of course, a better (and more expensive) solution is a chainguard on each side of the chainring. To be fair, I've had some gnarly crashes during races, and even then I did not lose a chain. I was running a short-cage Dura Ace rear derailleur, which has really good spring tension, plus I shortened the chain as much as possible. I suspect these two elements helped to keep the chain from derailing. The trick with the Third Eye is to locate it close enough to the chainring so that the chain cannot drop below it. The elevation of the Third Eye needs to be such that in the event of a chain derailment the chain will slide down the sloped surface and back onto the ring. This takes a bit of trial and error to get right. But honestly, I have not had a single problem with it.
I tried this same set up on my mountain bike and it was a complete disaster. I attribute this to excessive chain slack due to the longer chain that's required for the long-cage derailleur and the higher gear range of the cassette.