Has anyone noticed all the creepy pictures they used showing everybody slouching in chairs to try to use this? Because this is not a thumb-type device, think about the practical reality of using this as a "casual" device. You sit in a regular chair or recliner (as I am now) with your legs straight out. How do you plan to hold this thing? With an iPhone/iPod, you can easily hold with one hand and use. With this device, it is so big that you will not be able to use it comfortably in a chair without trying to prop your legs up.
Think about it in bed. I use the iPhone in bed most nights to read RSS feeds and watch some TV shows. I am honestly trying to think how I would hold this.
How about casual use in the kitchen? You basically will have to be standing over this thing to type as it slides across the counter. Maybe they should have considered rubber backing to help prevent this.
I agree that the keyboard/dock looks pretty cool. But, for a casual device - are you really going to pop out your keyboard and dock to use?
As I said in an earlier post, i see this as a niche device. I think it is too expensive for casual users in any big numbers. Remember - millions of us have already invested in an iPhone or iPod and also already have a laptop or PC. Apple is assuming that people will shell out another $500+ to add this into a very narrow usage pattern. I am sorry - I do not see it.