RE: What does a hybrid really do that a high end single cam doesn't ?
I will throw this out to answer the original question. I don't know, yet. I have been shooting my Mathews FeatherMax with original Max Cam for several years now, and I am currently shooting it better than I ever have. My average in our paper animal league is either 3rd or 4th highest out of 40 some guys and gals. This is shooting against many other hybrids (Hoyts) and several wheely bows. I have always had good flight, both with fieldpoints and broadheads. All that being said, I am really excited to get my new "hybrid" bow and see the differences.
I think for the nock travel, we have to take that with a grain of salt, as most of us have no way to truely measure it, ie expensive equipment. Therefore, we must rely on what the manufacturers tell us. Obviously solo's and dual's perform, as do the hybrids. I mean, how many solo cam bows were in the woods and at the line the past few years. Shoot what you want, and do what you can to take it to the next level.
It is archery, not rocket surgery (stolen from a dog trainer I know)
Have fun,
JMAC