Yeah, World 1 is definitely a continuation of Galaxy 1, which is understandable. You need to get your feet under you before the game literally takes the floor away in later Worlds.
But World 2 comes around... and things get going. I gotta say, I'm having a blast with this game. The music, the platforming, the atmosphere... really just awe inspiring. So far I have to say that this game is even better than the first, and the first is one of my top 3 games ever. It's just too good to be true.
Super Mario Galaxy 2 is awesome.