what's the fuss about flipping the disc?
flipping has been around since the cassette era, side A, side B
then came the LD era, either you flip it or change to disc B, unless your player has a auto reverse function.

Same with DVD era, LOTR EE, anyone? 2 bloody disc for the movie, and 2 more bloody disc for the features! My Seven Samurai disk is a D10, so I'll have to flip it the middle of the movie. It's nice to take a short break to refill your drink/snacks, take a pee, hump someone, masturbate and etc...
I doubt anyone would want to sit on their sofa continuously for more than 3 hours no matter how comfortable is it.

I'll say flipper has nothing to do with BD or HD-DVD format... yeah... some might say, Hey!! format X has bigger storage, thus it can squeeze in all of the goodies in one disc!! So no flipping needed!!
I'll say screw those people who is lazy arse to find an excuse not to lift their fat ass from the sofa.
2 discs, 4 discs, 2-sided doesn't matter to me, as long as the studio gives me a good quality movie with all the goodies, I don't mind getting up to swap disc or flip disc.
Hey, who knows? Maybe one day those player maker will come out with a player that has multiple tray with auto reverse features! Good for those fat arsed couch potatoes! You can sleep, eat, shit, and screw on your couch without the need to getting up!!