IGN has published their hands on review from the Nintendo Media Summit in San Francisco. From what I've read so far, their impressions are quite positive.
IGN Hands-On Review
A few interesting points:
The Smash Dojo has yet to reveal Norfair, so expect it to come soon (tomorrow?)As for the battlefields, there's the "Smash Battlefield", Delfino Plaza from Super Mario Sunshine, TP's Bridge of Eldin, the Halberd from Kirby, Yoshi's Island, Norfair (Metroid), Lylat Cruise from Star Fox, Pokemon Stadium 2, and Sky World from Kid Icarus.
Looks like characters are going to have costume changes..Since each character can also switch colors pre-fight, Nintendo took the opportunity to seamlessly include Dark Link as one of the character options. He fights the same, but looks totally badass, which is a must.
Metroids, Advanced Wars sprites, Drill Dozer..Other attacks we've seen already include a floating Metroid that sucks onto battlers, a massive attack of multiple 2D Advance Wars sprites, various Pokemon, a dashing Drill Dozer attack, the Excite Bike attack (similar to the Advance Wars move), and then of course the fire flower, baseball bat, beam sword, and the like.