"An obvious advantage of projecting from a Tablet PC is portability - I would have loved to walk around my classroom while I was presenting. Using wireless projectors, you will ultimately be able to walk down the whole aisle in assembly - although with current wireless data transfer speeds, there is a noticeable lag between writing something and seeing it appear on the projection screen.
"Every teacher has a different style, and people adapt to technology in different ways. What the Tablet PC does is provide more choices. My advice is to give it a go - try different approaches and see what works for you."