Unfortunately I do not have any of his speakers other than the Submersive (yet), however, I do know for a fact that he has worked with customers whose purchases have not quite met the mark (no pun intended). Earlier in the year, I know there was a fair bit of activity with home theater meets featuring Mark's products in the Chicago area. I expect that sometime soon there will be more as well. I would also post your request for user demo's on Mark's forum in addition to here, if anything for more coverage.
Lastly, know that he is at this time (and for the past few days) moving into a real commercial building and is likely just very busy getting things setup.
Not the best reasons overall, I can appreciate, but I will say this, having experienced some of his speakers vs. other lesser but respectable speakers, and having read the reviews of others who have more experience to equal or more expensive speakers, I think it is worth the patience, especially if your slant is towards Home Theater.
Thousands of experiments have conclusively proven that beating drums and clashing cymbals brings back the sun after a total eclipse.