Interwritemobi

My school will soon buy Interwritemobis. I used one three years ago and gave it up. I found them difficult to use and even worse my students found them tricky too!
They tell me they are easier now. Of course if they work it must be really interesting and the students will be more involved in what we are doing.
I suppose you have tried them. Are they really easy to use? What would you advise?