The permanent will keep any supertypes it previously had
He can be shifted for four, making him cheaper to play, and he lets you play a song card of cost four or less for free whenever he quests
Progenitus real strength was Natural Order, you could easily cheat it into play and short of a Wrath you would be winning two turns later
Wizards of the Coast tends to make common cards more simplistic in terms of abilities and mechanics, that's not to say that common cards don't deserve a place in your deck, just that your Rare or higher cards will likely allow you more opportunities to gain the upper hand in battles, or turn the tides
Games Games where Audino appears, in release order
Trainer's Pokemon got revealed, this mechanic is returning in the TCG