Lots of confusion and misplaced hostility on this product. Probably from people who are not interested in this item and don't really want one anyway. Understandable, but really, there's no reason to bag on something if you don't really know what it is, why it is, or how it is used.
I'm probably the target market for a product like this, as I am an artist that uses a Cintiq at work and I also have a Cintiq at home for freelance. I also draw on-location frequently and would love a portable computer with a stylus interface with sensitivity and performance that is comparable to the Cintiq. (By the way, the stylus interface is far far better than a touch screen surface here. Most artists are better draftsman with pencils than they are with their fingers.)
I bought a 21UX Cintiq when they first came out (back when they were unfortunately REALLY expensive) and have used it for years and it has actually paid for itself many times over. It is a fabulous product and has become almost a requirement in most animation and some film studios. Many artists (myself included) actually turn down job offers if I have to work on a graphire or intuos style table and not on a Cintiq. I have spent my whole life learning how to draw with a pencil on a paper, right in front of me, and Modbooks and Cintiqs simulate that experience pretty well.
Don't expect Apple to sue this company anytime soon- what they are doing is helping sell more Apple products and giving those products wider capabilities. Nothing that different than Carroll Shelby taking brand new Ford Mustangs and adding aftermarket items to make the cars faster and handle better.
However, what I am personally NOT a fan of on this Modbook is the price tag. With 3500 bucks, I could buy a 22" Cintiq, a small Macbook Pro AND an Ipad with a tablet drawing program thats pretty solid for on-site drawing. Its a great item, but the price is simply too high for what it is and what it can do in my opinion.