I think that you just use the disc once and you are all set, like a firmware update. Don't know why Sony couldn't just make a firmware update available. Maybe Netflix did all of the work and that is why it is coming from them.
No, for now the disc will have to be in the system. This was the quickest way for it to be deployed. In the future there may be a program download (there's a streaming music service in Europe which integrates this way).
I guess I'll find out tomorrow, but from what I've read so far, this is a BD-Live disc which connects to Netflix's service. Sony supposedly helped develop it, but I'm not sure why it wouldn't work in other players which have sufficiently fast BD-Java implementations. I'd like to hear from anyone who has a PS3 and an Oppo BDP-83 who gets this disc.
