I think HDCDs are already becoming obsolete because recent non-HDCDs are mostly well recorded, and much better than the recordings of even a few years old. I own an HDCD player, and though I can still tell the difference between HDCD and non-HDCD encoded CD's, the margin is slimming all the time. If you don't have an HDCD player, playing HDCD encoded disks that aren't properly decoded by the HDCD filter tend to sound worse than non encoded CD's, so there is a slight sonic penalty to be paid by not owning one.
