I am looking for high-quality conversion for a music server, with the ability to play the occassional SACD, DVD or Blu-Ray, and newly purchased CD without ripping it to my music server. I agree, Kr4, that if there is a pre/pro in the system, you can use a digital input and its internal DACs, but my goal would be to get the pre/pro out of the system. In my LR, space is limited, and I have an excellent setup for 2-channel sound, but I'm perfectly content with 2-channel movie playback and therefore don't need all the pre/pro functionality.
There are several examples of high-end, multi-format players with digital inputs. Simaudio, Linn and Wadia all provide players that do at least SACD and Redbook, plus a digital in, and the Linn SC does them all (minus Blu-Ray) with digital in. Esoteric and Ayre do not make players with digital inputs.
I would think a digital input would be one of the least expensive "formats" to support - no licensing, etc. - and provides a level of flexibility that many would want. In my case (and I'm sure others'), I would like to keep box count as low as possible, sound quality as high as possible, cost as low as possible, and flexibility as high as possible. Okay, I want it all :-)