If you like 8.9-inch screens, you might want to get one now. Asus has said that it'll be phasing out that size in 2009, since 10-inch models are dominating the market.
According to Digitimes,, president of 's Asia-Pacific division said that 10-inch models account for 95% of the company's sales. 7-inch models make up the other 5%.
To be honest, I'm surprised 8.9-inches is not a popular option. Maybe I'm just weird, but I always though that screen size hit the sweet spot between fitting into a purse and still having a somewhat usable keyboard.