I also have a two-channel SACD system (please see my "system" link for details). I'm very happy with it, and to be perfectly honest...9 out of 10 multichannel mixes that I've heard sound a little "gimmicky" to me. They have a tendency to throw random sounds around the room, almost as if the engineers were seeking the cheap thrill of multichannel for the sake of multichannel. I'm sure there are plenty of SACDs that use multichannel in a musically sound and proper manner, and I'm equally convinced that more high-quality multichannel SACDs are on the way. But for now, I think it's very much worth it to have a 2-channel SACD system, as even discs intended for a 5-channel mix (i.e., Pink Floyd's Dark Side of the Moon) sound far more convincing and engaging on a 2-speaker SACD setup than on mere redbook.
--Brian
--Brian