Pretty useless as of right now besides making smaller things easy to tame. After the tlc 2 update it's gonna be a mobile smithy and will have reduced carry weight for obsidian and other things. So next quetz and anky metal run bring an argy so you can grab obsidian and put it in argy.we all know the pain of getting boned by 1k weight of obsidian and having to drop it.
Getting a massive TLC update in March 2018. The saddle will act as a mobile smithy, Argentavis will be able to carry with Talons as well as with its beak, reduced carry weight on obsidian and a few other unannounced resources (similar to the mammoth and wood), and will also gain a Rapid HP Regen upon eating (likely from devouring corpses and not specifically food from inventory). Like so people can see!