I have the WD My Book World II. As you have read it has gotten mixed reviews, but IMO for its price point, it's a good value, and meets most of your wish list. It sustained throughput is slow, probably couldn't keep up with HD video playback, but does just fine streaming music up to full wav BW, playing photo slide shows, backing up files etc.
I think its weakest aspect is the supplied MioNet branded anywhere-by-web access software. I found it to be a memory and resource hog on the host PC, not very intuitive to use, and a little unstable so I un-installed it, and am using the box as a simple NAS. I read recently that WD has accquired MioNet, so maybe they will beef up the remote access app. We'll see.
Good luck in your search...