First and foremost, I think the tablet will be a really simple way for people to access the internet and email. That may sound silly in this day and age, but believe me a lot of people do not want to go through the hassle of getting broadband internet, configuring wireless access, figuring out whether to use client email or web email, and diagnosing where problems are when things aren't working. I envision the tablet to be sold like an iPhone - with connectivity and email configured before you leave the store.
Second is ebooks, magazines, and newspapers. The Kindle and the other readers have shown that this market is growing and has a large potential. The killers here are a readable screen, very light weight / easy to hold, and battery life. I expect good performance on the first two but wonder how much battery life they will get when balanced against these desires.
Finally, video. Anyone can watch video on a desktop or laptop computer and it's not bad. But it's not great either. Most computers are built as functional devices, not beautiful ones. They just don't have the clean look that consumer appliances like TVs do. Almost all TVs have hidden their control buttons and moved to a sleek border with few accents. This tablet will be similar - I bet you'll be able to prop it up (somehow!) and watch and not feel like you're bringing a keyboard, trackpad, and a bunch of buttons along for the ride.