The "Post-PC Era" doesn't exist. That's right, I said it. There are currently only two eras worth mentioning that are related to computing technology. Those are the PC Era (PCE) and that which I've termed "Before the PC Era" (BPCE). Apple fan boy or not you are still in the PC era and probably will be for the foreseeable future. Let me explain why.
Before the PC Era computers were large power thirsty refrigerator or larger sized devices. They often used vacuum tubes and required their own power plant to operate along with a team of experts, scientists, and fly swatters (Early computers were plagued with insects that would nest inside them near their heat generating parts, which is where we get the term "computer bug" from). Computers were nearly always purpose built and in the pre-PC era computers that were reprogrammable wasn't even necessarily a mainstream idea. This is something we all take for granted now-a-days when we quit playing Angry Birds and stop to check our facebook.
The Personal Computer Era
Then along came the PC, a small desktop sized machine that could do what larger machines could do before it at a fraction of the cost. Commodore, IBM, and Apple pioneered here with offerings all targeted at different markets and make not mistake, these *were* pioneers. No one knew whether anyone even wanted one of these machines in their home or business. Many other companies followed suit shortly after with copies and clones, all the while paving the way for one of the biggest explosions of technology the world has ever known. What the PC did to change business, culture, even life as we knew it was, rather is, incalculable.
The World Wide Web
Enter the Internet. Online services, bulletin board systems, and eventually the Internet connected these PCs into a global network that took the world by storm. Slow to start (the Internet was first opened to the public in the late 1980s) the Internet eventually became an integral part of most everyone's life, whether at home or work for business or pleasure. This amazing communications technology still relied (relies?) on the PC. Content made for the Internet is produced on PCs and the wires and bits that the Internet runs on are useless to humans without the interface a PC provides.
Parallel to these developments was another feat of technology, the mobile phone. The first mobile phones were large, clunky, and awkward devices, yet they demonstrated a capability that was previously only dreamt of in episodes of Star Trek. Through the years, mobile phones have been miniaturized and enhanced with features such as color LCD screens, QWERTY keyboards, and most important of all, connectivity to the Internet. The result of this integration of technologies was the smart phone. Developments in the mobile communications market opened door for wireless computer networks and the cornucopia of smart phones, net books, and tablet PCs that have recently come to market.
Still a PC Era
It may be simply a discussion of semantics, but PC stands for Personal Computer. A PC is a computing device that is small enough to be owned by a single person. This was true of the first desktop computers in the 1980s and it still applies to laptops, net books, smart phones, as it certainly does to tablets. These devices are still personally owned, reprogrammable computers that provide three features that allow us to interact with the Internet, a display, an input device, and a network connection. There will not be a Post-PC era until this model changes in some significant way.
The *real* Post-PC Era is when The Cloud becomes mainstream. When, instead of interfacing with a device, we interface with The Cloud, directly. Or maybe when the world around us is the computer and we interface with that instead, can we claim to be in the Post-PC Era. (Watson anyone?) This may sound a lot like something out of Star Trek, but think back to that first cellular phone and how radically different it was. This kind of technology may not be too far off but it is definitely not a mainstream reality quite yet.
None of this is to detract from the excellent job of creating hardware and services that Apple and their charismatic leader Steve Jobs have done in the past five years or so. They deserve to be recognized for their efforts but what they don't deserve (yet) is to be credited with the end of the PC Era.