Getting to look at the top card of your library, and eventually cast cards off of it, is always a useful effect
Drawing a card whenever you cast a spell with mana value 5 or greater is excellent with sweepers like pre-rotation Sunfall, where you can kill every creature and draw a card, with removal spells like Leyline Binding, or with the various Overlords that can enter the battlefield for cheap via impeding, like Overlord of the Hauntwoods
If you've got the creature token generator, you're in great shape
Many such cards have a triggered ability that transforms the card (when it's on the battlefield.) One of the most typical such ability is " at the beginning of each upkeep, if no spells were cast last turn, transform (this card) ." Many players actually don't realize that this is a normal triggered ability that uses the stack, and therefore can be responded to
Its worth is clearly demonstrated by recent auction results in 2024
What if I forget to stand up before declaring attackers