Resurrecting from the dead...
I'm reasonably sure that 2008 was their last year for using steam, since I was on it in 2008 and it was pulled by the steam engine, followed by my relief at having gone that year when they announced at the end of the season that they were going full diesel.
Amusingly enough, my trip on it was inspired by the DLRR and the Grand Canyon Diorama. I was flipping through a "greatest railway trips of the world" type coffee table book shortly after my last trip to DL in 2006 when I came on the entry for the GCRR. I was in shock: the Disney thing with the canyon and the steam train and stuff is for real?!
We rode in the Pullman carriages going up and Parlor Class going back. I will never by choice ride in a Pullman again, given that they were built for people with an average height of about a foot or more less than mine >_< Plus, Parlor Class is really, really nice. I would love to go back to the canyon and take the train, but this time forego the GCRR's vacation package and have an extra day or two at the canyon, maybe staying in the El Tovar.
Anyways, here is a video I cobbled together of the trip, for any interested persons: http://www.youtube.com/watch?v=d1qXLoFJ_CU
(Incidentally, the way back involved a 7-hour layover in LA, with an added bonus of it being a third Sunday. So Disney trains prompted the trip and closed it with a visit to Walt's Barn).