Watched it this morning and loved it, so it has reaffirmed that this is a day one purchase for me.
Plus there appears to be speculation about another game mode to be announced (maybe at E3) or maybe released later in the year as DLC. There certainly is a gap for it amongst the selection screen. My guess would be either Super Mario Bros 2 or Mario World 2: Yoshi's Island. The latter would look gorgeous in HD and would be like 3D World in that you have to start from scratch if you select it as it would have a completely different set-up.