If a permanent has no stun counters on it, it will untap as normal
Its a very versatile spell that will probably see some amount of play
For the sake of simplicity, think of a set as being split in five colors (yes, there are colorless cards, but let's ignore them for this example)
Thats some incredible card advantage for aggro decks
Of course the best thing to do with discard is often to set up your graveyard with cards you want to reanimate, or otherwise recur
It is one of my favourite mechanics so I cram it in where I can but in practice this is not able to compete as a stand alone module and is just there to support +1/+1 counters, infect, energy, and a few other bits and bobs