I saw the first trailer and thought: "He's cool... shame he's CGI, cos there's no way that can be a practical effect." Saw this and, judging from the audience gasps, they were all as amazed/pleased as me that the little guy is real.
I had no idea they had actually built it until just now! I totally thought it was just CGI. My mind is blown that we actually have the technology to build BB8!!!