I haven't made the leap to a SACD of DVD-A player yet. I'm sitting on the sidelines for awhile till a good 2nd or 3rd generation universal player comes around. I do deal with surround music in my work, however.
I personally do not really like to have an active center channel when playing multi channel music, preferring to have a 'phantom' center. One reason for this is the physical difference in the placement of the center speaker. Mine is lower than my main left and right speakers, other people may have it above the mains, on top of a TV or whatever. This is not ideal if a seamless soundfield is the goal. Phantom imaging is actually extremely good provided you sit in the 'sweet spot', and for me at least, the front soundstage is more seamless with the front speakers running in stereo.
That said, I haven't a clue about the mixdown capabilities of the current players for the center channel. It will certainly influence my purchase decisions when I am ready to buy. The player will have to have the option to disable the center channel for SACD and DVD-A, yet have the center channel in operation for movies, where I prefer to have a 'hard' center for dialog. I think that is going to be a tall order, and I'm not holding my breath for one player to come along that meets all my needs.
I think in the end, I am going to have to design and construct a simple summing 'mixer' to do the job, with a switch to enable or disable the center speaker accordingly. Such a project would only require a few op-amps.