Hooked up the Xbox One yesterday. You route your cable box (AT&T Uverse for me) through the Xbox. With the Kinect it's pretty sweet. You just say "Xbox On," and it turns on my Samsung TV & Yamaha Receiver with the xbox. You can just say "Xbox watch TV" and it pops open the TV app. "Watch Comedy central" and it changes channels.
It doesn't appear that xbox is capable of passing an unaltered bitstream. I could choose from "uncompressed 5.1" or "Bitstream" with a choice of DD or DTS. Either way the Xbox is decoding the sound and reencoding it to send it out. I don't think this really matters for me.
I haven't set up Plex on it yet, but I've been impressed with Pandora & Xbox Music. I purchased Forza Horizons 2 and was thoroughly unimpressed with the download\install time. It was a 37GB download and from start to being able to play took about 5 hours. A Steam game of the same size takes considerably less time.