This new offering from Nintendo is not the same as previous efforts. It is a combination of the Gameboy systems adventure play as well as stadium battling. BUT beware that in order to multiplayer battle you need Gameboy Advance,cables and games to play head to head. Colosseum itself will not play head to head with the Gamecube controllers. Additional, Colesseum does not offer "rental" pokemon to battle with. You need to capture any Pokemon you intend to battle with. You and a friend can not simple select 6 pokemon to battle. You have to import from a gameboy for one player and use the captured Pokemon for the other player. You can not just multiplay quick battle. We called Nintendo and it seems this was the way it was meant to play.
In its favour though the graphics are good and the tunes are fun.
I strongly recommend you rent this game first before you purchase. You may find it is not for you.