I have been a owner of the iPhone since the first edition came out. It is by far the best phone I have ever used. I do not imagine myself using another phone for years to come.
Before the iPhone, I changed my cell phone every year. I loved the new Sony Ericssons especially. If a new model came out, I sold my old one to buy the new one.
Then the iPhone came out. I was never an Apple fanatic. Didn't own anything from Apple besides the iPod. Long story short, I've had the iPhone and converted from a lifelong PC user to a Macbook Pro.
Apple has the largest apps store on the market. The types of apps available are endless. I have an app that lets me send free international text messages with my girlfriend, who lives in Taiwan. I can make free phone calls with Skype. I use Yelp often when I travel to look for great restaurants or worthwhile sightseeing attractions. I'm not going to go into much detail about the different types of apps because it would take a whole book. It's no surprise the iPhone app store is the largest one because it's the best.
The iPhone 4 now has Facetime and that will become the standard for most smartphones in the future. It's video chatting on your phone. The iPhone has a front facing camera that you hold up when you talk. Your video is in the corner while you see their video on the screen. You can push a button and it'll switch to the rear camera to show them something. You can walk around and talk. Both people have to have an iPhone 4 or the latest generation iPod touch. Using Facetime is free all over the world! I've used it to talk to my girlfriend. Another way I get free long distance phone calls. Both users have to be on Wi-fi to use Facetime.
Now you can record HD videos up to 720P. Looks amazing when played back. Great to record memories of kids or vacation. Users have shot movies and commercials just with their iPhones! The videos you record can be posted on Youtube, Facebook, or e-mailed right away. Amazing.
5 megapixel camera
A long time ago we had to carry a cell phone and a digital camera. Those days are over. Now with a 5 megapixel camera, you can take great pictures and just carry one device. I went traveling in October all over the US and this was the first time I shot the majority of my pictures on my iPhone. Hard to tell the difference. On the iPhone you can immediately edit your photo and email it. My favorite photo editing apps are Camera+, CameraBag, and Best Camera. It's so convenient.
Google Maps with GPS
When I travel, Google maps is my most trusted companion. I can locate where I am and how to get to where I want to go. I can search for public transit or driving directions. With the built in compass on Google Maps, I can see which direction I'm facing, Helpful when I'm in a big city like New York City and need to know which way to walk coming out of the subway. You can bookmark places so bringing them up when you need directions is simple.
Going from the older iPhones to the iPhone 4, I definitely noticed how crisp and clear the new display was. Webpages and photos looks more sharp. Playing movies on it makes it your pocket sized HD theater screen.
These are just some of the main features I love about the iPhone. Of course it holds music, videos and makes phone calls. However the above features makes it truly my favorite phone I have ever used. Every year Apple comes out with a newer iPhone model and the features keep getting better and better. I'll be an iPhone user for many more years to come.