There is no need to opt in, every steem account will be copied, username, password, profile settings (image, etc) but the Stake (same as Steem Power) will be the same as a fresh new account, equal to the VESTS by number, and your reputation will be at the 25 level, though I think I am going to change that to the raw unit with K, M, G, T, P (thousand, million, billion, trillion, quadrillion). The reputation scores actually are normalised logarithmically to the 0-80 or so, but I think that exposing all these underlying values will be more motivating to users.