I'm also curious to know reasons behind not considering a hard drive based system. Most of the people I've noticed that have negative views of HD Based systems, are the ones that haven't tried it.Yes there's always a chance of losing a drive.But this is what backups are made for.
Once solid state HDs become the norm and cheap. I believe more will be willing to change over to HD based systems.
I can tell you once you go that way..there's no going back to a disc player. I don't own a disc player in the entire place! These days you can stream your content in HiDef to the display of choice. Everyone in my household has access to the media collection! That's 10,000 songs and over 500 ripped Blu-rays and DVDs.
I can watch a movie on the big-screen as my significant other watches a recorded TV show in the bedroom and the kids watch a movie of their choice in their rooms. All of this streamed from the same Media server at the same time.
Shoot..throw the disc in the basement and surf the collection on HD. Or if you just can't let go of the Disc. Buy a changer and link it to the HD based system! Control the collection remotely!
Although the last suggestion is very possible and some use this. I personally don't see the need for the extra mechanical wear , when it isn't necessary.