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i was using a sonyericcsson p800 the a p910 which were some of the first smart phones. they blew in comparison so was very happy to use a 3gs for the last year and a half. just bought an unlocked 4 and couldnt be happier. the user interface is so intuitive and smooth its unreal.and ios5 looks like it will make it that much more refined
 
The quote below pretty much sums it up for me, my last Phone was a Palm Treo, paid for by work. I had my calendar, contacts and other data in that phone. My work stopped paying for a phone so I was in the market, I have never been unhappy with any of my Apple equipment so jmping to an iPhone was just a natural way to go.

Wirelessly posted (Mozilla/5.0 (iPhone; U; CPU iPhone OS 4_3_3 like Mac OS X; en-us) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8J2 Safari/6533.18.5)

For me it's the intigration of hardware and software. Apple designs the product and the software that runs on it. I also like the fact they control (lock down) the device. I seldom worry about viruses/bugs/etc. It just works.

The hardware is a source of pride for Apple. They really go out of their way to provide eloquently feeling devices. They have the money and resources to provide top notch products at less than what can be provided by the competition.

Finally, the ecosystem. As a personal user, I use my iPhone mainly for the experience. I dont require exchange service through work. I can check my email, surf the web, share contacts, etc effortlessly. The investment in music, movies, apps, etc also keep me squarely on the Apple side.

It doesn't hurt I use Apple computers and have iPads as well.
 
I bought it because it was the only phone that appealed to me, and I had the money. I had just gotten my first paycheck (15 years old at the time!) and instead of saving it, I spent it on a brand new iPhone 8GB a month after they came out! :)

I've switched away a few times (Samsung Focus, Bold 9700, Nexus One), but always come screaming back to the iPhone. It just works.
 
I don't own an iPhone yet but have used an iPod touch for 3 years. I plan to get the next generation iPhone for the same reasons given by others. It just works with the other Mac products. Plus the investment in apps and familiarity with the op system will certainly keep me in the Apple family. NB; I don't consider myself an Apple "fan boy".
 
At the time of buying my Droid X, there was no iPhone for Verizon (7/15/10).

I just recently switched to an iPhone 4 for Verizon. Why? Because everything else sucks. Literally. Let me elaborate on that.

First off, Blackberry. Great phone at first, but overtime it began to freeze A LOT. It's slow, the app store is pathetic, and BBM gets old pretty quick. The low resolution tiny screens and plastic feel gets to be of an annoyance.

Second off, Android. My Droid X was great, at first. I loved that phone, the gorgeous 4.3" display made viewing web pages extremely easy. The app store was okay. Over time, the updates made the phone worse, and Google could give a **** about being quick to fix it. My phone went from awesome to a piece of ****. It froze, all the time. Random service drops when I had full bars, web pages didn't load even though I had full service, it would take black pictures, the camera gallery always crashed, the phone itself became slow even after multiple resets. The wow factor of the screen size wears off too. Oh and as for flash player? Yeah, it's extremely laggy/choppy and crashes all the time. You have to be on wi-fi for it to actually be usable. To top it all off, the speaker on the Droid X is unbearably low, crappy quality, and just a joke in general.

After a year of having my Droid X, I switched to an iPhone (6/5/11). It's only been a few weeks, but I love this phone. The screen is so fantastic it's insane. The colors are amazing, and the pixel density is crazy. It's beautiful. The build quality is also fantastic. It's high quality glass, encased in aluminum. It's ultra thin also. The design is extremely unique, you can tell a lot of work was put into it. It feels very high quality. The speaker on the phone is loud too, which is a bonus. The OS is awesome, I actually like the way the notifications are delivered, I have no complaints about that. The apps are far better than Android's too. The front facing camera is VGA, but pretty good quality. The back camera is simply amazing at 5 megapixels. Very good quality (I own a DSLR, and this phone has really good picture quality). It's fast too. No slow downs. All in all, this phone is amazing, and IMO, the best one out there.
 
I was already a mac user and was looking to replace my blackberry. I had a friend with an iPhone 3G and I played with is a few times then decided to buy one. Skipped the 3Gs and got a 4 when it came out last year.

At the time it seemed the best choice and it still does for my personal needs in a phone. I like how it works so well with my computer at home. And as many have pointed out, at this juncture I have a lot of $ invested in apps so as long as something really crushing doesn't come along I will be an iPhone user for years to come.
 
The iPhone was best in class, and is still excellent. Switching to an iPhone a while ago, I've found very little reason to leave and a lot to stay.
 
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