From the literature, it appears they are "mixing" between the 5 or 7 channels instead of sending them discretely to the correct speaker such that , say for a situation where your rear left surround is to far back, a small amount of the signal for that speaker would be sent to the left side surround so that the "image" of the sound would come forward from the actual speaker position slightly.

So they create virtual speaker locations using your actual speaker. It will work well in situations where your speakers are off ideal positioning in the horizontal plane, but physics ain't gonna change where one speaker in the system is too high.

The Audyssey in my system had a pretty noticeable effect. I have a 6.1 setup (two rear surrounds, the 6 comes from going phantom center, not single rear channel), but my speakers are placed basically in the exact recommended symmetry and position, so it is mainly correcting for acoustic issues of the room, not placement.

That said, it definitely improved the surround experience in my system. I ran for nearly 7 months without it, so I was well acquainted with the Onkyo 885's sound in my setup before I ran the correction and began using it.

It sounds like the Trinnov is at least a comparable system, so unless your room is spot on for spec and treated with very good acoustic control, I would bet most would find it a positive feature at least for HT. On SACD, I disable all the processing.