To be honest, I rarely use phones. I text, Tweet, message, but I rarely call up people in my contact list for a chat. In the past week, I've made exactly two calls but that doesn't change the fact that this smartphone has significantly impacted my life.
For my uses, the iPhone is a mini-tablet with a very good screen, that's got a phone app.
2. Translation Apps I teach ESL, so I'm always checking for accurate translations using my iPad. Now, I can do most of this on the fly, without typing anything, using Siri. I simply use the following pattern "what is XXX in Chinese" and Siri will pull up a good translation using Wolfram Alpha. It's quick and works well when you run into certain words that are closely related to others, yet have different meanings.
3. Online Anywhere I'm not a fan of email, and since I run Inbox Zero (successfully for more than 2 years), I rarely need to check my email more than a couple of times a day. However, being able to get online with a device that has a good screen, like most smartphones, is very useful. Most of the time, I'll be running Facebook, Twitter, and Instagram. These can be quite useful if you're wondering what's happening in town when you haven't made any plans. Also, it allows for quick Google searches, running apps that need online access etc.
4. Tethering While tethering is somewhat limited with Verizon in the US, since you have to sign up for the "Mobile Hotspot" option that can cost $30 per month alone, this isn't the case in Asia. My monthly plan, costing about $45 includes this by default. I can tether my iPad to my iPhone, and do the same with my laptop. It's extremely useful, if you venture into areas like the suburbs which don't have reliable free WiFi. Unless you plan on getting 3G cards for most of your tech, this option is definitely worth it.
5. Photos DSLRs can be get bulky, and when you can take good photos with a very small and thin device, which are almost as good as ones taken with popular point-and-shoot cameras, you can basically cut down on the weight you carry around and the devices you need. For iOS users, and soon Android users, Instagram is one of the best ways of sharing everyday photos. It's become easy now to take photos everyday, without much of a fuss. Smartphones allow for quick sharing through Twitter, Facebook, and other sites, which is very convenient if you tend to do this with your photos.
(Images: Flickr member John Salvador licensed for use under Creative Commons, Flickr member Alexis Didier licensed for use under Creative Commons and Flickr member Miki Yoshihito licensed for use under Creative Commons)