I bought this a while ago with the purposed of using with my Sony Bravia KDL-46HX820 and my HTPC.
Firstly, I find the sound on this is very thin, even after the tweaks to the settings that people have suggested. Even my old logitech PC speakers sound way better for music.
Secondly, I wanted to use HDMI pass-through with the HTPC connected to the s401 and passing through to the TV. If I connect the HTPC to the TV then pass optical to the s401 the TV converts the surround sound to stereo hence wanting to use HDMI pass-through. When connecting this way I found that video was laggy when using the HTPC. So I took it to the Yamaha service centre here.
Then ensued a couple of months of back and forward emails where Yamaha wouldn't test it properly and just claimed that it must be the TV for ... reason, then when I explain how they are wrong because of ... reason, then they say it must be the HTPC for ... reason, then I explain they are wrong again for ... reason. This went back and forward. Then the guy at the service centre actually replicated the issue on multiple PCs and found that the s401 making the PC switch the refresh rate from the normal 60Hz to 30Hz, which does not happen when directly connected to the TV. So you can manually go and change the refresh rate to 60Hz and it will be ok again, but every time you switch import source on the TV, turn off the TV, or reboot the HTPC you have to keep manually changing the refresh rate. I haven't been able to find any kind of refresh rate locking program for Windows 7 that works. Argued some more with Yamaha that their box shouldn't be messing with anything to do with with the video part of the signal and if they don't want to fix it then I would like to return it for a refund, but in the end they just kind of gave up and said they don't officially support computers so too bad. So I am probably going to sell it.