30% of Play boosters (but, interestingly, not Collector boosters) have Art cards, and 5% of Play boosters have art cards with a gold-stamped artist signature or Planeswalker symbol
Nissa, Voice of Zendikar 7.5 A lovely little token generator
The three life you gain rarely makes much odds however and on that basis incinerate is the better card (despite helix being less playable in general anyway due to more restrictive colour requirements)
Instant speed is a huge deal, especially when you're trying to deal with a stack of Ocelot Pride tokens before they can attack
Its first ability pumps out Icy Manaliths that you dont have to sac like you do with Treasure
Third, the delay creates drama, a quality that I have respected more and more as I've advanced as a designer