For the Lesson cards, you will notice that they have a special icon in the upper left to make it easier to notice these cards when you have cast a spell with the new learn mechanic
This should give you a good idea of what any given card will sell for right now
6/6 is huge and hitting an opponent one time makes him twice as good, because you'll probably have one or two cards in your yard
So if you can sweep away all the Squirrels and Soul Sisters on your next turn you can essentially undo their combo and be no worse off
Not only do you discard the two best spells from your opponents hand, but they also need to find a way to kill this creature, potentially drawing removal out of them, if they find it at all
My ire was calmed when Avatar The Last Airbender was announced, though: I was more than happy to take the bad with the good