I suppose to an extent it does depend on your audio equipment. What do you usually listen to music through?
I can tell the difference between lower bitrate MP3s and V0 but not sure I'd be able to tell the difference between V0 and FLAC.
Video on the other hand I'm more picky. I hate poor quality video, or more so, video that should be better but isn't. I don't mind a mobile phone video being low quality, since that's the format/style.
I think my biggest gripe is with ITV Player online. Their catchup service is a shocking quality whereas I think the quality on BBC iPlayer is really quite good, and they even offer HD streams in places.