This card has been a staple of Modern artifacts decks ever since it's original printing in Lorwyn. It can really help accelerate creature-heavy decks by just enough to make them win. It's one of those cards that seems pretty bad, but it has a lot of uses that you don't think about right away. Basically, I like to think of this card as having the text "You may have a creature you control enter the battlefield tapped. If you do, add one mana of any color to your mana pool" because that's essentially what it does (except you can use it on other people's turns too).
Pros: Gives your slow creatures some usefulness
Cons: Only uses one creature, forces creature to tap
What? You thought I was going to look at Kiora? Not until at the cards in the set are officially spoiled!