Destructoid have had a hands-on with the game and cover all the phases once again, and include this interesting bit of information:
I also got some details on how the game's online infrastructure is going to work. Spore.com is going to host a catalog of user-created content ranging from creatures, to buildings to vehicles, which can be browsed and downloaded into your game world at will. There will however, also be something called the Sporecast, whereby a player can specify his of her preferences in terms of anything from civilization ideology, art style, or something as simple as creature color, and the game will search and download anything suitable it finds.
So it sounds as though the content might be downloadable via Spore.com just like The Sims, or you can use the auto-downloader which sounds like it might be optional. Pro-G have posted their own preview as well, though a little shorter than others.