DC does block out ISPs that require additional programs to run. The game is currently slated to ship about a week from now. My advice is that you and all your friends should quit listening to Sony's marketing department. The future stability of the Dreamcast will depend on current DC owners continuing to support the system via the purchase of software and new users buying the console. It is that simple.
Japan means absolutely nothing.
Just ask Nintendo. It will have great games. You can't play either one. Go have fun with your DC, and get your friends to do the same, and you'll be fine. You're looking good.