Today, for billions of people in the world, it’s impossible to imagine not having a smartphone. But even more than that, it’s impossible to imagine working without a smartphone. When I think about how I worked 10 years ago–in the days before the original iPhone was released–it seems like a century ago.

It’s not that there weren’t “smartphones” in the days before the iPhone; I had a Palm Treo and a whole lot of people had BlackBerries. They connected to pricey, slow cellular data networks and let you read and reply to email, no matter where you were. It was the cutting edge at the time. I do recall, however, that I only carried my big, bulky Treo with me when I was traveling out and about for business. It wasn’t on my person at all times, but if I needed to be in touch I would bring it along.

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The thing I remember the most about the day that I swapped my SIM card from my Treo into the original iPhone was that it was the day when carrying my phone with me went from being a burden that I tried to avoid whenever possible to being a treat. I always had my iPhone with me, and it was not a burden but a privilege to carry it. And so began my life of always being in touch with the rest of the world via a device I carry in my pocket.

Those old smartphones were email machines, and so they were relevant for people whose primary business was sending and receiving email. But the reason we think of the iPhone as a demarcation point is because it redefined what a smartphone is–a slab of glass with a touchscreen, full of apps to do just about anything you can think of. (Though the App Store didn’t debut until 2008, it’s hard to imagine the iPhone or any smartphone without third-party apps.)

At the time, Apple’s decision to release a phone without a hardware keyboard was greeted with howls of derision from BlackBerry addicts everywhere. I’m pretty sure that for people who were well versed in BlackBerry keyboards, today’s smartphone keyboards are still no match in terms of speed or reliability. (That’s why they still make smartphones with physical keys!)

Apple’s controversial decision proved to be the right one. Ditching the physical keyboard allowed a much bigger screen, which would be used for a software keyboard when necessary, but other purposes when it wasn’t needed. It also changed the terms of what the device was for: A BlackBerry or Treo was for text input, for email. An iPhone was for… anything? The keyboard was there when you needed it, but it wasn’t a core part of the product.

That said, the original iPhone software keyboard was a pretty amazing piece of software design. It dynamically altered the touch targets below the keycaps as you typed, making guesses about which letters were most likely to come next and which were not, which improved your chance of typing the right letters–and of course, it would suggest a word if you didn’t manage it. For the majority of users, the software keyboard has proven to be worth the trade-off. And it allowed Apple (and its competitors powered by Android) to reach international markets without alternate hardware tailored to each country’s preferred language or input system.

The original iPhone’s most important feature, the thing that pushed the entire device category over from being a bunch of blocky email machines into something else, had to be Safari. Phones in those days didn’t handle the web well; either they’d load dumbed-down WAP sites designed for phones with number pads, or they’d render pages badly. My memories of trying to load webpages on my Treo are a mix of terribly dithered graphics and completely broken page layouts.

It’s no mistake that Safari turned out to be a major portion of Steve Jobs’s original iPhone demo. A smartphone with a desktop-class browser was a huge deal. Pages (unless they contained Flash, of course) loaded on the iPhone just like they loaded on a Mac or PC. You could see, and interact with, the real web, not a pale imitation. The iPhone took a world intended for desktop computers and shrunk it down into a screen you could put in your pocket.

SEE: Apple’s first employee: The remarkable odyssey of Bill Fernandez (TechRepublic)

I do wonder sometimes about the impact that always-on device in our pockets has had on how we separate work and personal life from one another. It’s hard to beg off a work emergency when you can access anything on the internet from anywhere you might happen to be. But the flexibility these devices have given us can’t be denied. (And in some parts of the world, the smartphone is commonly a person’s only computing device–giving people access to the power of a computer and internet connection for the first time.)

Yes, you can now find me anywhere–but I can also go anywhere and be comfortable in the knowledge that I can be reached. Instead of chaining people to desks, work can be done in parks and cars and airports and long lines. Melding work and home lives doesn’t necessarily have to be a dystopian vision. It can be an empowering one, too. It’s all down to the details–and with any luck, our society is evolving to get those details right for business and worker alike.

Even if you would never be caught dead using an Apple product, it’s clear that 10 years after the iPhone (and nine years after the App Store), it set off a revolution that has given us power and connectivity that we never had before. It turns out that the entire personal-computer era, the one that I grew up in and that appeared to be on its way to change the world, was just a prelude. We live in year 10 of the smartphone era. Long may it reign.