Handoff and airdrop between devices is a game-changer for me. Both of these combine to let me be more efficient whether I'm working on an iPhone or an iPad. Both will become incredibly more powerful when Yosemite ships for Macintosh. 


Now I can ditch complexity in many of the instances when I previously used a clipboard sharing service or bookmarking service so I could get a link or a document to the correct device to finish the task at hand.