Has anyone used Grammaropolis?

I’m asking because homeschool buyers co-op is having a deal of the day where the forever pass for up to 5 children is half off.  The intro song I just listened to was rather irritating and I could hardly understand the words.  I am wondering if all of the songs are like that.  

Anyone have experience with this program?  Did you find it useful?  Why or why not?

https://www.homeschoolbuyersco-op.org/grammaropolis/?c=1