Just read the FAQ's and they do seem quite well written and explain as you said many questions on here, but if every company lived up to everything they promise you wouldn't have questions like this popping up.About half the questions in this thread could be answered by taking a look at the Leatt FAQ: http://www.leatt-brace.com/customer-support/faq/#383
I wear one every time I put on my full face helmet, along with a Dainese spine guard. It felt strange at first, but what doesn't? For me, the minor decrease in flexibility is more than compensated for by the confidence that I've done everything reasonably possible to protect my CNS, short of stopping riding. I wouldn't base what precautions I take on what WC pros are doing, for a number of reasons.
Some people don't buy that it'll do anything. Some people think it's fine to backflip a BMX out of concrete bowl with no helmet on. It's your personal decision, and you live with the consequences. What p*sses me off is people (either online or in person), who are not in full possesion of the facts, spouting their opinion aggressively or in a mocking way and putting people off who are considering buying a brace. It's out of line. Fair enough telling someone 'Oh these tyres/pedals/bars are sh!t', but don't try and persuade someone to take less precautions when it comes to safety equipment.
I do believe the Leatt is a good thing but people have opinions and some have owned one and found it restrictive enough to make it annoying, to them that may end up being more dangerous than not wearing it.
On a different note, wouldn't you be more likely to get spinal damage by copping a rock or a tree to the spine?