I heard it is better to connect the a/v source straight to the tv. If the a/v signal goes through a switching device it can degrade the picture and sound. My HR24 is connected to the tv (hdmi1), blue ray (hdmi2), PS3 component.
The optical out on HR24 is connected the optical in on the a/v tuner, that allows the tuner to decode 5.1. And I can turn off the tv and leave on the a/v tuner so I can listen to the music channels.
Not if it's HDMI. HDMI is all digital, so there's no 'degradation'. There's nothing between 1 and 0 so it's either there or it's not (this is also why it is completely unnecessary to pay $100 for an HDMI or optical cable). It's also a stretch to see any analog switching degradation on mid to higher end receivers as long as you use decent quality cables.
And I disagree with cparker on the scarcity of digital inputs on receivers. If anything they are MORE common nowadays. Even a $200 Sony has 3 HDMI, 3 component, 3 optical and 1 coaxial input, 6 analog AV inputs, AND it upconverts non-HD sources to 1080p. What is going away are obsolete connections like S-video, composite, 5.1 DVD, and tape/phono inputs. So if your turntable has a magnetic cartridge you'll need a pre-amp and it'll be labeled AUX, but you'll have no shortage of digital inputs. 3 optical + 1 coaxial is about the norm, because anything connected via HDMI already has a digital audio connection. That is usually assumed to be your set top box for cable/satellite, an Xbox or Roku/Boxee, and a PS3 or Blu Ray.