1. yes it is pressure sensitive
2. it only works where my wacom sensor is... basically that white block in the video.
3. i used the g4 because it has a broken motherboard and was virtually trash anyway. it only boots some of the time. Any laptop should work.
4. yes, it could be prettier. I know. I don't care.
5. yes writing on an lcd is bad for it. If it were to be used more often I would place a small plexiglass or lexan sheet over the screen.
There are many many people who want mac tablets. Also, many artists like to be able to draw directly on the screen. Wacom offers a product that does this, but it is $1,000 - $4,000 depending on size.
There is also a company that modifies mac laptops to be tablets here: modbook
While both are fantastic products and far superior to what I've made I can't afford either of those. So, I took an old mac laptop and a wacom intuos2 tablet and hacked them together. It was fun and serves its purpose well enough for me.