Is it really hard to get a bounce rate under 20%? I hear anything over 35% is cause for concern, 50% (above) is worrying."
I have a video site with bounce rate 20% (because people stay online to watch the videos, view related ones etc). A wallpaper site with bounce rate 30-35% and 2 blogs with bounce rate 45-50%.
It really depends on the niche of a site. Some sites want their bounce rate to be less than 25% and some wants it higher. For one of my site(music niche), it is 23% bounce rate percentage.