i think i heard that the pokemon wii game hooks up to your ds and imports pokemon you've unlocked in the ds games and then you can play against your friends online, sounds expensive to me though.
yeh, that was a bit off a duffer, although i heard that four swords zelda was supposed to be real good, but you need 4 gameboy advances and 4 cables and 4 friends, don't think i would get very far in that game somehow.
The only time I used it was to play Final Fantasy CC and to be honest it wasn't worth it. Using the d pad to control the characters was just too unresponsive. Plus the GBA's screen was too small and you had to hold the GBA right next to your eyes, often resulting in pulling the cable out of the gamecube!
know what you mean, i had a first generation gb advance (man, that screen was dark), i can remember plugging it in my GC for the tingle things in windwaker. it got boring quick, i couldn't see the screen either.