I currently have black electrical tape on more than 1 item sitting on my HT shelf (router, modem, etc). If you do a nice clean job with it, then you won't even notice it. I can tell you that on my setup, you won't see it, even when you are looking for it. The last time that I had a TWC tech in my house, the first thing he said is "your modem isn't working" b/c he couldn't see any lights and he couldn't see the black tape on it either.
I do agree, it isn't the ideal solution, but it can be done in a manner that is not conspicuous by any means.
Luckily, my Pio Elite AVR does have the option that the display goes off completely like 5 seconds after the last input.
I am also a person that really detests bright lights on my HT stack. Another option could be to open up the AVR and disconnect the wiring to the display. If you are lucky, it may even have a quick connect terminal that you can simply unplug. Wouldn't be the first time that I have done that either, or completely removed an offending LED. Again, not really ideal but gets the job done.