I didn't read the entire thread but I will say this: The Cowboys are doing this thing right.
I believe that this is Barber's last season in Dallas. I think, barring a phenomenal season, that Barber will be shown the door after the 2010 season. If they trade Choice, now, then they let a solid RB jump to another team after they put all the work in to make him a solid player. It's no secret that RBs can be had into the middle rounds of the draft, so it's not as if his production couldn't be replaced. But, the idea of turning the kid loose after putting all the work into him makes no sense.
Barber has little to no trade value, right now. No one wants his contract. Choice has trade value, but some fantastic upside. I hope the Cowboys play this thing out for the season and make changes in the backfield next year (namely, sending Barber down the road and going with Felix, Choice, and a draft pick).