I had one but had to give it up and let someone else use it. I am a big tech person... but I couldn't get the hang of the interwrite... I think it was more a coordination issue, than a tech issue. My problem was looking at the screen, while I wrote on the tablet. (My kids had probs with this too). I could see how great it would be to have one if I could walk and chew gum at the same time!!
I tried to use it for coordinate grid lesson, it has all kinds of templates you can use, I found the grid, and plotted some points... It was abandoned quickly by me. If I could have gotten the hang of writing on it, I can see how it woul dbe great ot use in every lesson! Hope you are better at it than me!!