This was a scary card back in its day and it's still kind of scary today. Remember Dryad Militant? With this guy, it's a 4/3 for 1. Esper Stormblade is now a 6/5 flyer, Empyrial Archangel is a 8/11, and Transguild Courier is an 8/8. See why this is scary yet? Honestly, the only issue is that it doesn't give the bonus to itself, which means it's a 2/2 vanilla for 4 on its own. Everything else about the card is great.
Pros: Gives bonuses to other multicolour creatures
Cons: No bonuses to itself, 2/2 for 4 on its own