As far as SD cards go, there is a card reader adaptor for photos and a USB connection for cameras, so we know the device can access external storage through the 30-pin connector. It'll be a question of file system support for other media or external drives, I guess?
Chill. It is widely rumored that multitasking will be added to the iPhone -- and presumably now the iPad too -- in the next major firmware update.
Also, I see several things it has that netbooks generally do not -- like a decent display and a processor that isn't hamster-powered.
Yup. The base model is exactly what I wanted. A kick-ass Web tablet + email device + ebook reader. Easy sell at $499.
Now, whether people will buy the full-boat models for $830 + whatever the accessory keyboard costs as a full-on laptop replacement, I do not know.