With some newly-revealed release dates, this spring/summer is shaping up to a great one for the 3DS -
May 20 - Mario Tennis Open
June 18 - Pokemon Conquest (regular DS game)
June 26 - Heroes of Ruin
July 3 - Theatrhythm : Final Fantasy
July 31 - Kingdom Hearts : Dream Drop Distance
With the possible exception of Mario Tennis, these are all day one games for me.
Ha, Mario Tennis is the only one I'm certain about!