So me and my friend are having this conversation about some product. He says it's great. I haven't tried it yet but I superficially disagree with him. Now that I have tried it, the conversation comes up again and he restates his opinion about the product and I respond with something like this.
"I agree with you about what you are saying about that product, now that I have tried it out myself".
Is agreeing with you ABOUT the correct usage of the word? Is the whole sentence grammatically correct?