I have been using I-Ready for 3 years. My entire class (6th grade) hates this website, and this includes my teachers. I have seen errors such as a right scalene triangle being a equilateral triangle, 7 * 10 being 80, and even multiple grammar issues in passages and text (it doesn't make you correct it). I don't remember the exact lessons, but trust me on this.
Also, the lessons (usually too easy for the students) take anywhere from 15 min - 1 hr. This is tiring and just wastes time. As my English teacher likes to say "Anything in school that does not benefit your education does not matter." (Which can be wrong but still)
By the way, it does NOT work on mobile browsers or Apple App Store. Currently I am typing this on my phone (my laptop is not available) so I can only show you the error.