The stat boost is a decent bonus, but more often than not we'll be sending the aura right back where it came from so we have it ready for the next volley of removal
It obviously works well when you have multiple copies, but even on its own, a 1-mana 2/1 in an aggressive artifact-based deck is still very good
Snapcaster Mage Snapcaster Mage went from the best blue creature ever and a blue staple across multiple formats to a barely playable card
The extra nice part is that while Stellas trigger can go off each turn, the exiled card remains playable until your next turn giving lands and sorceries a much higher rate of usability and allowing you to potentially bank up spells for a flurry on your next turn
Magic Arcana - May 23, 2005 - Wayback Machine Magic Invitational 2006 Coverage Broken Link 2006 Magic Invitational Coverage Ruel Invokes Invitationalists For Victory - May 10-12, 2006 - Wayback Machine Thank Your Lucky All-Stars
Stax and Prison strategies often require you to play enchantments that slow the game down, or that prevent you from being attacked