Maybe I'm not a right person to judge, since I was eager to have such a thing when I first heard about it some three years ago, so I was not the one who needs to be convinced I need it. Now when I have it, I don't see a reason ever to listen with just two speakers anymore.
There is a big difference between center of soundfield created in your brain and having the same thing exist in reality. In short, it is also helpful fighting standing waves, it adds more power and speakers in the system making it more capable. It's own coloration seems to be extremely low. I can easily hear differences between a few great preamplifiers with Trinaural. I guess those would be masked if Trinaural will have more of it's own distortions.
Drawback may be that if you have a smaller space, center speaker will always be in different acoustic environment than two side speakers (being much nearer to the wall behind). It helps with standing waves, but center speaker sound different when you listen to speakers separately. I don't know whether such thinking is "built in" into Trinaural, but effect of this isn't noticeable when playing music. However I found that it seems center speaker and sides need slightly different tuning. Maybe Mr. Cheney can give us some general rules for tuning of VMPS in Trinaural.