Smart Notebook App Worth It?

I think Smart Notebook is a really versatile program both for my needs as a teacher and for my students' needs.  In fact they will often choose it as their "go to" program to demonstrate their learning.

I am wondering about the Smart Notebook app for the iPad and would it be worth purchasing (at $7.00 per iPad)?  I am thinking it might take the place of purchasing some other apps, and be in a format that I and my students would be familiar with.  For example: we could create base ten blocks in Smart Notebook and students could use those to show their work rather than purchasing the base 10 app.

Thanks for any input/opinions you might be able to provide.

Scott