I think that the "real world" probably is another matrix in the matrix, but i do think that the point of Mr. Smith downloading into the brain is not a piece of evidence. I think it's not because if you brain is "plugged" into the matrix, its kinda like running a VPN server, or basicly, like file sharing for the brain. If you are killed in the matrix, you die. The body can not live without the mind. So if he downloads into someones brain, wouldn't he just be a virus in the head?
lol.. mabye crazy people in real life aren't really crazy... they just have a computer virus in the head... j/k
but seriously... even if we were in a matrix.. we would have no idea...... So many things to ponder.... not enough time.