Few would argue that the iPhone was a game-changer when it launched in the U.S. on June 29, 2007 -- for years ago today. The iPhone was officially unveiled by Steve Jobs at Macworld earlier that year and Apple fans were eagerly awaiting the day when they could finally get their hands on the device. Stores shut down at 2:00 pm and customers begin lining up in droves for the 6:00 pm launch. Just like the iPhone 4 launch, there were happy customers, clapping Apple employees and sold out inventory.

Apple activated 146,000 devices in the first weekend of sales, a staggering number for back then. Most people grabbed the 8 GB model ($599), a situation that likely led Apple todiscontinue the 4 GB model in September 2007. Apple also slashed the price of 8 GB iPhone price and caused an uproar among the early adopter crowd.

The iPhone skyrocketed to the top of the smartphone market because it was radically different from its competition. At that time, some of the top smartphones in the U.S. market were the Treo 755P (a Palm OS champ for CMDA carriers), the BlackBerry Curve 8300 and the Windows Mobile-powered HTC 8925 (TyTN). It was a market dominated by QWERTY keyboards, trackballs and small touchscreens that needed a stylus. User interfaces were clunky and hardware design was secondary to functionality. BlackBerry and Windows Mobile ruled the market and Palm was beginning its slow descent. This is the world Apple entered four years ago.

The original iPhone was radical. It had a full touchscreen that you could use with your fat fingers. With no stylus or trackball, users touched icons on its screen. After years of tiny menus and small X buttons in the corner, the iPhone offered a UI with large, lovely icons and a simple menu system. A touch-based interface is passe now, but it was groundbreaking four years ago.

The iPhone had a web browser that beat any competitor on the market and robust multimedia functions that made music and photo fans drool. Previous smartphones like the Curve and the TyTN focused on PIM connectivity. It was all about email and syncing your contacts and calendar. The iPhone stepped away from that paradigm and focused on the fun stuff -- web browsing, music, photos and video. It did have email and PIM functionality like its competitors, but it did that and more. And yes, it was an EDGE handset and required you to sync via iTunes, but its forward-looking focus was on the internet and multimedia.

From a hardware perspective, the iPhone design was amazing. If you don't believe me, look at other handsets in 2007. Its predecessor, the Motorola Q, tried to redefine thin, but it looked more like a skinny brick than a carefully crafted handset. The HTC and Palm offerings were bland and, quite frankly, all looked alike. Once again, the iPhone was much different.

The original model had a whopping 3.5-inch display that was gorgeous compared to other smartphones on the market. It had a curved, slick design with just enough weight and balance to feel comfortable in your hands. It had a revolutionary multitouch user interface that used gestures to navigate.

And as a lot of early reviews point out, the iPhone just works. There's no fussing with an SD card and worrying about internal versus external memory. No need to pull the battery to prevent your phone from locking up. The iPhone worked and people loved it. Yes, there wereglitches, activation problems and missing features, but overall, the iPhone was the best first generation product to hit the market.

I, sadly, was not part of this early revolution. I lived and continue to live in an area that does not have AT&T service. I have used all the iPhone models, more or less as glorified iPod touches, but never experienced the excitement of getting the first model on the first day. Four years ago today, I clung to my Motorola Q and watched the iPhone launch from afar.

But that is me, what about you? Were you there on day one, ready to change the world with the iPhone? Or did you jump in with the 3G, the 3GS or even the iPhone 4 like I did? On the anniversary of its launch, let us know your thoughts on the original iPhone and its legacy in the comments. You can also reminisce by watching some YouTube videos shot during the launch. Enjoy!