Overall, I think this is a solid RC truck and good value.
First, yes, the truck is fairly large. It's probably best suited for outdoor environments unless you have a large indoor space. I thought it was fast for its size, and handled well. I have tested the truck on various terrain: pavement, tall grass, gravel, and wet areas. I can confirm that it is indeed amphibious! I drove the truck along the shallow edges of my pond, and didn't have any issues. In deeper waters, the truck seems somewhat buoyant, but just know that it's not going to handle like a boat. It does best in shallow water areas. I'd say it's very waterproof based on my tests.