In response to Yuk
"What are the coordinates of the hill you crawl down in first gear?"
It's the Walterdale Hill in Edmonton (the hill from 109th Street down to the Walterdale bridge), a major route into downtown Edmonton. In normal traffic conditions I go down that hill in 3rd gear with almost no braking.
The only times it's happened have been on that hill, when the air temperature was low (though the car is well warmed up by that point) and it's had the stock Michelin Pilot HX MXM4 tires on. For some reason it has never happened with winter tires on - which may be a coincidence, or maybe not. It could be that these tires have a very low rolling resistance and can build up enough speed and therefore torque to pop it out of gear.
Interestingly all the Honda reports concerning transmissions popping out of gear mention low temperatures - which is definitely the case here.
The dealer was going to try duplicating the problem with another V6 6MT Accord Sedan over the winter but all they did was ask other owners if they had problems - and none were aware of any.
One of my friends has an Acura TL which has a similar size V6, also with a 6MT. It stays in gear down that hill. Honda says that doesn't count because the TL has a different suspension.
FWIW the 6MT is said to be a low problem transmission. But it was only offered for one year in the Accord Sedan. I wonder if the heavier sedan has identified a problem that doesn't occur in the lighter coupes. And I wonder if all those supposedly trouble-free 6MT Sedans would pop out of gear under the same conditions. If I didn't have that hill on the way to work I'd think the new transmission was wonderful too.
By the way, aside from the transmission problems, I like the car a lot. Rides nice, handles well, there's room for four adults and it gets decent mileage.
2007 Honda Accord V6 6MT
2000 BMW 528i 5MT Sport