OS X Yosemite is going to start looking more like iOS. This isn't necessarily a bad thing. There are a lot of people who started with an iPhone or iPad before getting their first Mac. Making the app icons look the same across platforms helps make some things easier. For example, why is the current iTunes icon in Mavericks blue and on iOS it's red?
Another thing that is cool is how Apple is making iOS devices aware of when they are close to a Mac. They showed the example of starting an email on one device and then finishing it on another. I'm not saying that happens a lot but it looks cool. The thing I'm surprised about is using this technology for messages and phone calls. How cool is it that now your Mac can get regular SMS messages and place and receive phone calls? Your iOS device just needs to be in the house.
It looks like Apple has addressed the issue of sharing iTunes media and apps. As long as everyone is in the same house and using the same credit card on iTunes Apple has made it easier to share stuff. Plus if you have kids you can set it up so they need your permission to buy something.
And finally, Airdrop comes to the Mac along with iCloud Drive and cheaper cloud storage fees.