I failed to mention KAMI somehow, one of my all-time favorites (though 32 bit and probably not getting updated). KAMI 2 was recently released, uses the same mechanics, and is also enjoyable. Trilogic was part of Apple's indie promo and also good (and cheap). I also grabbed Blyss when it was Apple's free app of the week and am enjoying that.
So many good mobile puzzlers. I could easily do a couple more twenty-game lists.