Exactly. "You no more "die" when the cells or atoms in your brain are replaced than a river dries up when all the water molecules you could see at one point in time flow away." when we find a way to measure this little death relative to the bigger more permanent one we can make interesting arguments. My advice, assume the transporter/uploading-machine will kill you. You will use it anyway for the same reason you use a credit card at the grocery store or corner market, you will be worried that the people behind you will be annoyed by the delay caused from your hesitation and the person who comes out the other side will not begrudge you for creating them.
Replacement with the subtly different is interpreted by our minds as "change". You no more "die" when the cells or atoms in your brain are replaced than a river dries up when all the water molecules you could see at one point in time flow away.