edbro, I am writing from what I have seen personally:
#1. On at least one occasion I have replied to a new poster (1 post) with the skepticism that you describe, using the very terms that you describe.
#2. The reason I have done this, as a fellow customer and without any connection or encouragement from J River, is that I have personally read the flaming, pretexting posts that I originally thought came from a handful of malcontents, but which apparently come from ONE GUY. The guy I'm thinking of DOES register new identities from time to time and try to make hay out of non-issues. If you go to the AVS Forum and make a post with "J River Media Center" in the subject line, this guy will log in within a day or so and start ranting. I know that the moderators there have start deleting his posts wholesale, perhaps they have even banned him.
#3. Speaking for myself only, I don't post to an audio software forum to exercise my free-speech rights. And while I appreciate a lively exchange of views, I MUCH prefer the tone on the MC forum, and the general focus on A/V issues and how amazingly cool MC is--subject to bug reports. If you don't think it's cool, why did you buy it? After all, you had 30 days to test it out. I am constantly amazed at the number of people out there who think that other people's sites ought to respect their supposed right to rant at will and have it saved to their server. Where did this come from? If you want to speak your mind without restriction, why don't you just open up your own MySpace site and have at it? This is J River's house, which they're opening up to us, providing you make a minimal effort to mention how cool MC is.