There's been a lot of (occasionally controversial) talk recently about the "iOS-ification of OS X", especially as new apps and features (Notes, Reminders, Messages, Notification Center) are brought over from iOS to OS X Mountain Lion (10.8).
Talk of turning one OS into another is completely missing the point. What matters isn't the operating system, it's the data. To Apple, I'm a perfect user: I have an iPhone, iPad and MacBook, and I use all three for different purposes, but I use often use the same applications on all three. The iPhone is my portable computing device - it's with me all the time. The iPad is my personal device. I do basically the same things with it as I do on my phone, but around the house, since it is essentially the same thing but with a bigger screen. My MacBook is for working - I develop code on it, I write on it, but other than that it is really just a store for my music and photos, and that will end sooner or later.
The data is what matters, and Apple realises this, as shown by their approach to iCloud. Steve Jobs mentioned this change of approach, moving away from the desktop computer as your "digital hub", in his final keynote in June 2011, and that, probably not coincidentally since I've watched that video, is how I see it too. My photos will be stored, not now but eventually, in iCloud (permanently, not just Photo Stream). I'll be able to organise them, edit them and show them on whatever device I like, and keep the changes in sync.
I said before how I use my devices - portable, home, and work. For a long time people have talked about being able to move seamlessly between devices, and have an image of logging into a different computer and seeing the same window layout that they left behind:
When I left home, I was typing this article in a Word document on my Windows 7 desktop. The Word window occupied one half of one of my two huge desktop monitors. Splashed across the rest of the screens were several tab-filled Chrome windows, a few IM windows, and my text-based notepad.
When I later opened up my MacBook Air, I could access the Word file and my text notepad through Dropbox. But I had to make my computer do so. In a perfect syncing scenario, my laptop would know what I had been doing on my desktop and would offer to open up the right windows for me, preferably in the identical places on the screen...
Other than the ridiculous idea of having the same window layout on two large monitors as on a MacBook Air, this is still the wrong approach, because what people want is to be able to access the same data. The quote above, from Farhad Manjoo at PandoDaily, describes moving between two devices that let him write in the same Word file. All that matters here is that you can load up the same app and find the same thing in the same place, for example the text and the cursor location being the same. A perfect example of this is Tweet Marker. I use this on my iPhone, iPad and Mac, and I can jump between Twitter clients on all three of these and always pick up where I left off. The clients look different on all devices, even though I use Tweetbot on two, and used to use Twitterrific on all three.
So who cares that OS X is becoming "more like the iPad"? There will always be things that will be brought in the other direction, over to iOS, such as better photo management or video editing. Things are being added to OS X that let us pick up where we left off, and things are being added to iOS that will make it a stronger OS, and more of a replacement for a laptop (for most people), as time goes on.