Viva Pinata was without a doubt, the best game released last year. It's a lot of fun to play, extremely original, very cute and really addictive. Unfortunately it suffers from the same problem as all of Rares recent games.
It's too childish looking for most 360 owners, and Nintendo fans refuse to even give it a chance because it's not a Nintendo game. Though rumours have it that a DS sequel will be coming soon. Microsoft want it to be a big franchise, and it's almost guaranteed to happen on the DS.
Oh, and yes. You can smash the Pinatas, but the objective is to run a good garden to attract rare and valuable species to come in, smashing them wouldn't be a good idea, but it can often help to smash apart some of the more irritating species that come into your garden merely to make a mess. There's a demo on Xbox Live now. Anyone who likes the Sims/Harvest Moon/Animal Crossing should really give it a try.