It was my understanding that Spotify's home page generally shows global trends and probably sponsored content, at least it's pretty obvious for me because as you point out it's filled with artists and music genres I never listen to.

There's however plenty of automatically generated customized playlists available next to that. When you create a playlist it also recommends tracks it thinks will fit etc... I haven't found any obvious bias in those so far and they often recommend obscure old tracks that I doubt anybody cares to promote anymore.

Social playlists are where it's at. Expect Spotify to further leverage social and friend features.