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The market is hungry for today's iPhone launch. Existing iPhone customers are ready to upgrade. Nearly a third of Android users are would consider switching to iPhone, but only 11% of iPhone users would give it up. Sprint is making a big bet to become the third major U.S. carrier.

Apple just announced the iPhone 4S, a significant update to the iPhone's existing design. The iPhone 4 far outshone its predecessors, and a bump to that phone will surely prove popular. More importantly, the iPhone 4S is now a "worldphone." It contains both GSM and CDMA radios, so all carriers can now support the same hardware. Furthermore, the old iPhone 3GS is now free with a contract. But several Android phone manufacturers are neck and neck with Apple, and most of the mobile world doesn't even have a smartphone yet. Amidst the world's many phones, smart and dumb, where does the iPhone stand?

Instagram pushed out version 2.0.1 of its mega-popular, iOS-only photo-sharing app today. In addition to routine bug-fixing and a few other minor features, the update makes changes to two of the app's photo filters, which were overhauled with the release of Instagram 2.0 two weeks go.

It was the 2.0 upgrade that offered Instagram users the most dramatic reworking of the app's camera feature yet. In addition to changes to the camera UI and some performance tweaks, the filters in particular were totally rewritten to enable users to preview them before snapping the photo. The team also rolled out four new filters.

Serendipitous Web discovery engine StumbleUpon has released version 2.0 of its iOS app. The update adds the Explore Box, a search box that suggests new topics to stumble, and faster page loading. The iPhone app also received a significant interface overhaul, adding side-to-side page swiping and less cluttered navigation.

We already found StumbleUpon for iPad to be like a magic carpet ride for your brain, and the addition of the Explore Box will make discovery even faster. The Explore Box launched for the StumbleUpon Web version in August.

When it comes to designing its overall mobile user experience, Apple apparently knows how to keep customers happy. Almost 90% of people that own an iPhone say they'd prefer to stick with Apple when it comes time to purchase their next mobile device, according to a recent survey conducted by UBS Investment Research.

This is far higher than the retention rate for the second most popular handset maker, which was HTC. The Taiwanese smartphone manufacturer has managed to encourage 39% of its current customers to stick with them for their next device.

Instagram, the beloved photo-sharing app for iPhone users, has launched its biggest overhaul yet. Version 2.0, which is now available in the App Store, offers a redesigned user interface, four new filters, optional image borders and a list of new enhancements to the app's camera.

The new version of the app introduces "a complete upgrade to Instagram's camera with a brand new technology layer," reads a company blog post. Indeed, the UI of the camera itself looks completely different, with control buttons across the top of the screen and a new sample image for the filters along the bottom.

Apple fans and the technology press have been wondering aloud for months about what new features will be included in the next iteration of the iPhone. As the iPhone 5's rumored October launch gets closer, that speculation grows more feverish, as details are leaked and rumors turn into facts.

We're reaching that point with the iPhone 5 (or is it iPhone 4s? Or both?), which is widely expected to launch within a matter of weeks. With a barrage of new rumors and purported leaks everyday, it's hard to know for sure what's true. A few things are practically guaranteed: the phone will be faster with upgraded tech specs. It will probably have a better camera than the iPhone 4. One thing that's always been unclear is whether the device will support NFC.

Inkstagram, a third-party Web client for beloved iPhone photo-sharing app Instagram, has added user-created hashtag albums to its browser-based photo gallery. Instagram offers hashtags as a way of browsing photos, but Inkstagram's galleries are an original feature built on top of them. Users can create galleries for hashtags as persistent, shareable Web pages that pull in all existing Instagram photos with the correct tags. The gallery page also displays its number of views and a list of related galleries for browsing.

Carel van Apeldoorn, Inkstagram's managing director, says that 300,000 unique Instagram users - around 3% of the total - have connected their accounts to Inkstagram. The third-party service has many competitors, but hashtag galleries stand out as a compelling new way to browse photos on Instagram.

Formspring, the ask-me-anything Q&A social network, has just launched its first native iOS app. The big new feature for Formspring is photo sharing, which is incorporated into both questions and answers from the app. The iOS interface builds nicely on the website's UI makeover and new community features added earlier this year.

Formspring's Sarahjane Sacchetti says that the app is focused on keeping things "super-simple" for users in order to drive more activity. It's built around posting questions, answering, and viewing content from friends. Formspring says that over 75% of traffic to their existing mobile website comes from iOS, so this more powerful native app should see rapid adoption among Formspring's current users.

Apple's new subscription rules requiring publishers to fork over 30% of revenue generated from apps in the iTunes Store have claimed their biggest victim to date. As of last night, the iPhone and iPad apps for the Financial Times went missing from the App Store.

The new rules have not thrilled publishers, but reactions have been mixed. Some media companies, like Hulu and the New York Times, have decided to play along with Apple and offer a significant cut of their subscription revenue to the tech giant in exchange for access to millions of iTunes customers. Others, like Amazon, have opted to build HTML5 Web apps as a way to circumvent the new rules.

If you've ever felt underwhelmed by the Web browsing experience on the iPhone, perhaps MoboTap can help. The company just launched an iOS version of its Dolphin Browser, a third party mobile Web browser popular among Android users.

In addition to touting a very Chrome-esque tabbed browsing interface, Dolphin has re-imagined the way that sites and pages are called up and explored within a mobile browser. Its "Speed Dial" feature allows you to designate a page as a favorite, much like you can do with your phone's contacts. This is in addition to standard bookmarks, which Dolphin also has.