Its a set that can shake up Standard by easing decks into a third color, providing more deckbuilding possibilities and value
I like weird forced combat decks, and building ones centered around giving away tokens was so much fun to brew
Again, adds to your counters and gives you something to do with them
If it copies a creature, Spark Double enters with a +1/+1 counter on it, plus any counters that will be put on it from abilities it copied and other abilities of other objects
After all, uh, you've got to be fairly heroic to willingly run up 59 flights of stairs to save your friend
Of course, casting a spell that has transmute certainly counts as casting a spell, though transmute is completely irrelevant in that case