There's no way Spore could've delivered on its promises. But in spite of its kiddie-pool-shallow gameplay and occasionally boneheaded design, Spore's emphasis on empowering the act of creating and sharing on such a grand scale makes it totally one of a kind. Disappointed gamers can rail at Will Wright for appealing to "casuals" and for turning their ubergame into a shallow hodgepodge of genres. They'll be missing the point.
Bottom Line: As a game, Spore's a shallow but reasonably entertaining experience, but as an interactive toybox-meets-art kit, there's nothing quite like it. Occasional bugs and controversial DRM sour the purchase (don't pirate, kids), but never detract much from the game itself. Oh, and the procedurally-generated soundtrack by Brian Eno is freaking sublime.
Recommendation: Buy it. It might not be the "Sim-Everything" you were promised, but don't be surprised to find yourself loving Spore for a whole other galaxy of reasons.