Had a friend that got Phantasy Star Online in an auction and sure enough he could play it online. I'm not sure it that stands for all the games though.
Have they kept the servers up? I thought Sega announced they would be shutting the DC servers down at a later date.
Never got the broadband adapter, but I used it with dial up a couple times just to see the web browsing. Not a problem since I bought the keyboard for Typing of the Dead. I have the mouse, too, but don't think I ever used it.