I want one and so does my wife. We both have an iPhone 3G currently and a Macbook.
I have been promising my wife one for a while, she wanted to spend $400 on an ebook reader but from all the iTablet rumours, ebook functionality seemed pretty concrete so I convinced her to wait. I'll get her a 16GB wifi version, should be sufficient for her.
My iPhone 3G 8GB is maxed out from 50mb of photos, 300mb of songs, no videos or podcasts anymore and a ton of apps. While I want one, not sure if I've got the money in the budget for it this year. If I were to get one I would get one with 3G as I'm on the road constantly, and to ensure I have ample space a 64GB would be the best decision.