IMO, the most profound change this card brings is the surprise value. For example, Otyughs and Maxwell's Demons can pop out and instantly kill a creature, whereas before the opponent had a one-turn warning. This makes spells less unique in their ability to surprise, and makes Precognition more useful because you don't want to be caught off guard.
Second, many more decks can become viable because they no longer need to splash off-color quanta.
Also, you can use a creature's ability multiple times in the same turn by casting the shard after it's used its ability.