I used to have and HDCD capapable player but replaced it with one without the chip. I would agree, generally with ncarv's statement above. Most of the HDCD's that I have I would describe as being fairly well recorded. That being said, I could not discern any real negative difference going from the HDCD player to the non HDCD player that I currently use. There was perhaps a bit more "spatial information" or "air" on the HDCD player, but it was a tough call to make, certainly not an "in your face" audible difference. So my answer would be that HDCD discs should not sound worse on an HDCD machine.
Do HDCDs sound terrible on non HDCD players?
Being an analog guy I have but a small collection of CDs and only a handfull are HDCD encoded. All of them sound terrible on my non HDCD player with thick lower midranges, smeared, closed-in textures and a general lack of cohesiveness. For reference my player is the original Rega Planet and the HDCDs are as follows: Olu Dara, In This World, Steve Earle, El Corazon, Garcia and Grisman, Shady Grove, Neil Young, Silver and Gold. Any opininons?