Sacred Seven is your typical "Boy has awesome powers but can't use them until someone else gives him the ability" shounen anime. You've probably seen the same thing happen in anime like Bleach. The storyline follows Aruma, who fits the above cliche by being an outcast with a reputation for violence.
Story: With this type of storyline, you have the protagonist joining an organization to fight terrible, ancient monsters that threaten the world around him (that surprisingly didn't seem to catch his notice before hand...). In Sacred Seven, those monsters are Darkstones, and aside from HellBrick, they all seem intent on destroying the world. Aside from the fighting aspect of the anime, Aruma (now being able to use his powers) is gaining acceptance at his school. Apparently, teen angst is a turn off to everyone. And because it's produced by Sunrise, there's a mech too.
Animation: The anime is well animated, and considering it came from Sunrise, it's not too surprising. The battle sequences and the school activities are both done with excellent detail.
Sound: It sets the tone for the battle sequences, backstory flash backs, and lulling areas of school life. And the title of the OP fits the anime rather nicely (Stone Cold by FictionJunction)
Characters: As much shounen cliche as the series has, it does a fairly good job at developing the important characters. While at times, they seem to be cookie-cutter perfect for whatever shounen role they need to play, teh back stories allow them to have some sense of individual personalities.