Hi! We are starting Investigations in 5th grade next year as well. This year, I tried out the fractions unit (replacing the chapter in our current book) The kids really loved it. They learned so much. The problem for me was the amount of time it took. We teach in a Middle School setting, so I teach 3 periods of math-different classes. Our periods are only 39 minutes long and there is no hope of changing the schedule. So, if you have an hour of math time, I think you will find it wonderful!