Dealing one damage and buffing your turn-two play are both solid effects, and the back half of the card is a surprisingly powerful creature that can get in for hasty damage while denying your opponent any fun graveyard effects they might have planned
Like most Magic: The Gathering cards, the value of Island depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Foundations)
Its very rare for an entire table to be on Infect, so your life total will keep mattering to the players who do not want to deal Infect damage, making the downside of Leeches potentially worse than its upside
Even when not utilizing an infinite combo, Bloodthirsty Conqueror makes games feel completely one-sided from the moment it hits the battlefield
Similarly, an ability of another card that instructs you to "transform" one of these cards will cause you to convert it, even if that ability doesn't use the word "convert." More Than Meets the Eye notes: "More Than Meets the Eye [cost]" means "You may cast this card converted by paying [cost] rather than its mana cost." It functions in any zone from which the spell can be cast