Re: Classic monsters return (spoilers)
I'd say there is a good bet that Sontarans kept their appearance intact(though now shrunk down) mostly for the humor factor of being these action-figurey purple and small potato-heads juxtaposed against their curt and aggressive attitude. The Daleks kept theirs because they're Daleks and they're an actual icon of the show. Ice Warriors were a bad design to begin with and their redesign somehow looks worse, I assume again for some sort of irony when the suit comes off. The Draconians could benefit from a lot of polish but nothing about the design is necessarily 'bad', just unrefined and badly executed.
"There is no reason why good cannot triumph as often as evil. The triumph of anything is a matter of organization. If there are such things as angels, I hope that they are organized along the lines of the Maffia." - Winston Niles Rumfoord.