One of Apple's marketing terms is the idea of the "post PC" device. It has had some criticism, because the iPad has to be connected to a PC before you can use it, but I think that talking about the need to sync with iTunes on a PC is (perhaps deliberately) missing the point. Neither is it about the way devices are marketed; the way Apple markets iOS devices isn't about presenting a list of stats or features, inviting buyers to shop by spreadsheet in the way they might do for a new laptop, comparing CPU speed, hard drive size etc. I think its true that the killer features of iPads and iPhones (and MacBooks, come to that) don't come across on a spreadsheet- as John Gruber said, a MacBook Pro might be faster than an iPad, but the iPad feels faster. But that's just the marketing — it's about how the product is packaged, but that doesn't really change what the product actually is.
As a user of "digital media" you need some kind of a "digital hub"; you want your music, your photos, your contacts, and your documents to be together. (Not necessarily all of them together, but you don't want half your music collection on one machine and the other half somewhere else.) Today, for most of these things, that "hub" is probably your home PC. For some things (email, contacts and calendar, for example) your "hub" might have moved online. An iPad (or iPod, smartphone, netbook etc.) isn't a good device to use as a "hub" for these things for a number of reasons; not enough storage space, easy to lose/break etc.
But if your "hub" is online (or "in the cloud") then you probably aren't looking for a new and better "hub" in a phone, tablet or other new toy; you're looking for a new interface.
That's what "post PC" is really about. When your music collection lives on a server (whether that is a media server in your home, or an online service like Spotify) then you don't need a "personal computer" to connect to it. You want it on your phone, your stereo system in your living room, the radio in your kitchen. The idea that an iPad can't be "post-PC" because it feels like a PC peripheral seems backward to me; I store my music on my computer, but I listen to it on my iPhone, or on a wireless device that pulls it to my stereo. I store my photos on my computer, but I look at them on my phone, or an iPad, or on my TV screen, or a digital photo frame. Video that I record lives on my computer's hard drive, but they rarely get played back on my laptop's screen; they are uploaded to YouTube, burnt to DVD, or copied to other more portable devices.
Today, devices like smartphones, tablets and MP3 players are becoming the "main" devices that we use, while the PC is increasingly doing the job of a kind of server; it takes the photos off your camera, the music off your CDs (and maybe soon the videos off your DVDs) and pushes them out to where you want them. The PC, like the printer, is becoming a peripheral device as it hits its limits of mobility/portability, and smartphones and tablets take centre stage.
Horace Dediu at Asymco has a good overview of the "Post-PC" idea, talking about the progression of the PC up to and including this latest shift, where he comes to this conclusion;
I might add that the consequences of each generational shift are:
- Consumption increases
- Skill required decreases
- Support required decreases
- There are new applications and use cases
- The economics are not favorable for incumbents
- The economics are favorable for new entrants
- The older generation slowly fades through diminished growth but never disappears
I think that final point is the key one to bear in mind. Personally, most of what I do with my computer is stuff I just can't do with a tablet— but it's specialised tasks that involve specialised tools like development environments, FTP, code editors etc. There isn't a technical reason that a tablet couldn't run professional applications to do these jobs— it is more to do with the economics of developing niche tools for a (currently) relatively small potential market. But I don't think it will be all that long before, for home users at first and later more professional/productivity applications, the mouse and (full sized) keyboard stop being generic elements of a "personal computer" and become specialised tools for specialised tasks.