So far the Swift programming language looks like the coolest feature but I'm kind of surprised to see Apple rather than Google make a push for a new programming language.
Oracle owns the Java language through the purchase of Sun Microsystems and is suing Google for copyright infringement for using it in Android. Google won the right to use it in 2012 but the lawsuit was overturned in May of this year.
Java syntax is fine but I never liked it as a platform. Part of me always hoped Google would have picked up the pieces of Borland Delphi (based on Object Pascal) and ran with it.

Swift looks terrible. They started the conference hailing the 13-year-old developer in the audience, and while everyone in the security world grapples with the mistake of writing everything in "low-level" (read: overflow/buffer/etc impossible nightmares everywhere), Apple waste all our time by making yet-another low-level mistake language, complete with mandatory casting, unnecessary datatyping, bitlevel manipulations, and so forth.
It's hard to understand, full of pointless extra work for no reason, still unnecessarily verbose, and puts us all back into the security context of 1980, again.
We need FEWER languages, not more!

Flat? It looks atrocious. And goes against all Steve Jobs believed in for appearance. He would roll over in his grave - and worse is that it's Jony who introduced this....."Et Tu, Brutus" ? Then fall.. OSX"

This is a huge step backwards for me I am living in a third world country where Internet speeds are very slow. I already have huge problems with an outdated OS and Apps that can't be updated because everything depends on having a good internet connection. The problems get worse all the time. And I can't just order a DVD like before. I recently had to reinstall the OS and the only one I have is on a USB stick. I installed the OS and eventually got all my data back but now I can't use iPhoto and other apps because I have a newer version than the OS so I can't access any of my 5,000 plus pictures until I find a way to get the same OS version I had before. It looks like Yosemite will be completely unusable for me and millions of others in a similar situation. That is if I can install it in the first place. Apple has become a computer and OS only for those with fast internet connections. The rest of have a lot of equipment that is rapidly becoming unusable.

Still think it is miles ahead of the nightmare of Windows8. My whole work place and the workplaces I deal with can not work with windows8 and all the hoops of fire we have to jump through to make things work and happen. We all had to pay and re-install every single workstation with Windows7 64bit. It was expensive yet.. we still all fight over using the MAC systems that are in place. Whine all you want about Apple, we (and there is a lot of We) still work better with Apple since the big boss started buying them. We have to use the PC's as well unfortunately till we make a complete switch over. As for security.. it's all hackable. Proven in the last competition held in Vegas. p.s Not sold on the look but the features are cool

It makes sense for Apple to rationalize all their products into a coherent platform. I like the calling features from my computer, as well as the texting to non-Apple users. Makes me wonder what took them so long to pull it all together.
I agree the flat look is atrocious, and beyond what Jobs had in mind. It actually hurts my eyes. I want smooth design, not flat reality.
Still, instead of these pretty tricks and pulling its platform together, I wish they would tighten up the quality control on their MacBook Air and train their "geniuses" better. Apple's customer care isn't what it used to be, and I don't foresee continuing to buy their products or services until they shape up again.

FLAT is probably required so that Apple can make it easier to shift into a pre-3D vertial world/workspace; then they can add the 3D back as they add their own software updates...
This will also help their iPhone & iPad platforms sync with their vastly more powerful Apple laptops and desktop computers...
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I hope they are getting away from the gray font that is hard for many user to read and enable important Apps. like Contacts to display fonts in several sizes instead of having to resort to zooming.

Ive's genius seems limited to 3D shapes. Flat (modern?) is pedestrian at best. Its promoters seem to want to put graphic designers out of work. Any child could design flat UI's and I surmise that that is the real intent behind it.
Anything to get more apps developed. Flat is about marketing, not esthetics and anyone who can't see Job's priorities in that is missing the point.

When I upgraded(?) to Mavericks it behaved so non-Apple, I replaced the hard drive in my MacBook Pro. I reinstalled Mountain Lion on a bigger, faster Hybrid HD and put the Mavericks contaminated one in a drawer.
I guess I will dig out the toxic Mavericks hard drive, this Northern hemisphere Fall, and upgrade it to Yosemite. Afterward, I can always put it back in the drawer and happily return to using this superbly designed and elegant performing Apple product called OS-X Mountain Lion.

Instead of going after Google, I'd like to see more focus on Yosemite becoming replacing Windows as the defacto OS. To me, Apple is a product and interface company, not a data and service company.
"Google is getting better at design faster than Apple is getting better at web services" - Patrick Gibson (I think).