What size tablet do people here prefer?
5"=== a large smartphone/pmp
7"=== a giant smartphone/pmp or a tiny netbook (sans keyboard)
8.9"== a size between 7" and 10"
10"=== a size roughly equivalent to netbooks

What aspect ratio do people prefer?
4:3 === squarish so it is evenly balanced, easy to hold one-handedly in landscape for extended periods (eg ebooks)
16: 9 == rectangular so movies look great, fits webpages much more comfortably, games (eg 3D/racing) can have the controls tucked in the side in landscape mode for better experience. But its not as evenly balanced and makes it less convenient to hold with one hand in landscape mode for extensive periods.