They are really good. I've only ever heard vinyl that had had heavy play, and the cd masterings are good, but the SACD really shine in the way that SACD CAN shine, which for me is mainly a more vivid dynamic contrast, and a very open but not harsh high frequency range.
They also made a point of recording great music with outstanding soloists, orchestras and conductors. And that pays off.
Since I moved my Denon DCD-A100 to Dad's system I'm listening to a lot of SACDs and Redbook also sounds excellent sent via coaxial from the CL-5 into the Denon's excellent 32 bit DAC section.
Right now listening to disc 7 from this 8 SACD set.

Beautiful sound. I would say I prefer the Vegh Quartet performances by a hair, and especially love their cellist, but the sound and the ensemble playing on this cycle is exceptional. And I think I paid less than 40 dollars for 8 SACDs.