Transmission flushes are a huge controversy among some automotive newsgroups. The usenet group I was formerly associated with constantly bantered with this issue. It piqued my interest and I checked with three of my professional mechanic/service writer friends (2 in independent facilities, 1 at a dealer, not Acura). They all perform tranny flushes as part of their routine work, but they all said they would never, ever flush the tranny in their own cars, or recommend them to friends and families. They have seen unexplained transmission problems pop up frequently after a tranny flush; so often that they can't help but make a correlation. Beause no one has a definitive and provable theory, and it is a big money maker, their facilities continue its use. One of these guys theorize that because the problems show up more likely on older cars, that it may have something to do with higher than normal fluid pressures and strong solvents that end up dislodging gum and varnish. This is the purpose of a flush, but then these clumps travel into small passageways and through tiny valves and consequently partially or fully plug up the openings. They all agree that a simple, multiple drain and fill will fully exchange the transmission fluid. But interestingly, two of the three don't plan to ever have their transmission fluid changed. That even though it flies in the face of every service recommendation, they said they see more problems when people try to "maintain" their transmission, than to just check the level occasionally and leave it alone for the life of the car. Cleaning out tranny pans and replacing filters (MDX has no tranny filter) and pan gaskets, flushing, all seemed to introduce issues and problems. Ironically, the more experienced of the three (22+ yrs) felt that, based on long-term customers, the more often a transmission is serviced, the more likely it will suffer a catastrophic failure in its later years.
Yes, the failures could be blamed on the mechanics, maybe they blow sand grit up into the tranny when the pan is off or something. I don't know, I'm not completely convinced, but the controversy is not isolated, and its enough to make me cautious. For now, no flushes for me. I just got a case of Honda ATF oil for $32 (reg $54) and will just do my own safe and secure triple drain (nice parts guys, gave me a gallon of VTM fluid for free, because it was the last one and was dirty on the outside, but still sealed below the cap).