There are pros and cons to using a tablet pc as a reader. I currently own a motion ls800, motion m1400, and a sony reader. With regards to the tablets, it is difficult if not impossible to read w/them like you would a regular book because of the heat and weight. After ~20 mins w/the motions my arms get tired (and hot) and I need to set the unit down on the desk. Ofcourse the upside to using a tablet is that you never have to worry about what format your media is in because pcs can support pretty much anything. If you are a pure reader I would suggest an eink device or consider the nokia 770.
I LOVE MY SONY READER!