When Apple realeased iOS last year, it also introduced iCloud. iCloud allows seamless sync of contact, calendar, mail, photos, and documents (iWork) between iOS devices. Add a contact on your iPhone and immediately have it appear on your iPad. Take a photo with your iPhone and seconds later watch it on your iPad. Apple did bring some of the sync capability to OS X Lion but it was limited to contacts and calendar. I could not, for example, create a document in Page on the Mac and continue editing on my iPad. First, I had to upload it to iCloud via Safari. With OS X Mountain Lion, the circle is complete.
>One key addition is Documents in the Cloud. In iOS 5, apps like Pages take advantage of automatic saving to iCloud. With OS X Mountain Lion, the circle is complete as all documents in the iWork suite of apps will save this way as well. (via [TechCrunch](http://techcrunch.com/2012/02/16/os-x-mountain-lion/))
>In OS X Mountain Lion, sign in once with your Apple ID and iCloud is automatically set up across your Mac.1 That means right away iCloud keeps your mail, calendars, contacts, documents, and more up to date on every device you use. So when you add, delete, or edit something on your Mac, it happens on your iPad, iPhone, and iPod touch. And vice versa. (source [Apple](http://www.apple.com/macosx/mountain-lion/features.html#icloud))
So now, I can work from any Apple device! I expect third-party app developers will update their OS X and iOS apps to take advantage of the feature. OS X Mountain Lion is starting to look like iOS.
The three apps – Messages, Reminders, Notes – were introduced with iOS 5. On iOS, Messages allow iPhone (iPad) users to text each other for free. The Notes and Reminders app on iOS 5 sync back to the notes and reminders section of the OS X Mail client. With Mountain Lion, this apps gets separate treatment as a stand alone app along with Reminders.
iOS 5 introduced a new notification system for the iPhone and iPad. This notification system now comes to OS X. I wonder what the Growl developers are thinking right now?
I don’t know too much about this one except that Apple will require developers who want to sell apps in the Mac App Store to register and digital sign their software. One notable feature is that users will get to choose whether to allow apps developed independently of the Mac App Store onto their Macs.
>Apple wants to help you steer clear of malware even when you download applications from places other than the Mac App Store. That’s why Apple created the Developer ID. As part of the Mac Developer Program, Apple gives developers a unique Developer ID for signing their apps. A developer’s digital signature allows Gatekeeper to verify that their app is not known malware and that it hasn’t been tampered with. If an app doesn’t have a Developer ID associated with it, Gatekeeper can let you know before you install it. It’s another step Apple takes to keep your Mac safe. (source [Apple](http://www.apple.com/macosx/mountain-lion/security.html))