I may not have the experience you're looking for either, but the reason we pulled DS6 out of his public school 1st grade was because his un-skipped, un-accelerated classroom was making him miserable. His learning stalled, his attitude was lousy, and he was no longer the sunny boy we had sent to school. (Sound familiar?)

We had to make a change, and it was good for him.

We're home schooling now, but what we're doing with him really does amount to at least a full-grade skip plus extra subject acceleration in reading and science. (Maybe more than one grade--I'm not using a packaged curriculum for anything but math, so I'm not sure at what level he's operating right now. He's in the middle of a reading-level test right now so I can get a better sense of his comprehension.)
To be clear: I certainly don't think school should be all about entertainment for a kid, and I'm absolutely pro-work ethic. Not all of of life is fun and games, and I don't think a teacher's job is to dance like a clown to keep kids' attention...
...BUT I also feel just as strongly that boredom and misery don't have to be present to make that work-ethic thing happen. In fact, I think they're 100% opposed to developing a good work ethic. If you're bored and miserable, you're going to learn to hate work, not to find the joy in it. How does that teach a kid anything except to avoid work? Why would anyone want to work if all they know is that it's boring and makes them feel bad about themselves?
And I'd love to ask those who told you that "He doesn't get to decide he doesn't like school"...Why doesn't he? All kids--ND and GT alike--know from birth know what they like and don't like. I know that for me, one of the things I hope to help my kids to find is work that is fulfilling for them, work that is a reflection of their life and values, work that feels good--fun!--to them to do. Why should school be any different than what I hope for them to have in the rest of their life? They have values and goals now, so why shouldn't school mesh with that? I don't know why people make that out to be some sort of power struggle and that you'd be a pushover if you respected his feelings about school. I just don't buy it.
I guess what I'm saying is that there's a difference between the spoiled kid who hates school because he always gets his way at home and he doesn't at school (which seems to be what the "make him stick it out" people are assuming is the problem), and the kid who hates school because he WANTS to work and think but doesn't get to at school (which seems to be what's really going on). Two very different issues! I think you're right that a lack of challenge in school is not going to do your son any favors.
FWIW, our DS6 is working so much harder and is so much happier since we took him out of the regular classroom. He loves the more challenging work. He's sunny and happy again. And he's not winning some power struggle; I'm much tougher on him than his teacher was! (Albeit in more effective ways...)
It seems to me that you have some extra issues to deal with in your son's case. I'm not sure I'm clear on what exactly those are, however--does your son have an LD, or is he just asynchronous? That will affect your best course of action, of course.
Maybe you could clarify for me?
Happy Holidays!