We have finished 3 weeks of Eastern Hemisphere. Prior to this we used Sonlight. Actually, I am still using Sonlight for my younger son, BookShark for older. It's very, very similar.
What I like better is that I don't have to purchase their bible or LA materials, it doesn't have the missionary books which we did read before but were never favorites, it replaces those with some great biographies (like one about Nelson Mandela). It is almost identical to Sonlight besides what I have mentioned. It is also a 4-day schedule, which I love.
Since it doesn't include bible or LA, the IG is much less visually cluttered which helps me make the most of it.
I LOVE BookShark!