Messaging, App Store, Browser
With the arrival of iOS 5 and the iPhone 4S comes iMessage, Apple's competitor to RIM's vaunted BlackBerry Messenger system. iMessage integrates with the iPhone's SMS app, and allows iPhone users to message other iPhone users (as well as iPod touch and iPad owners) without incurring SMS charges from their carrier. It supports multimedia files, read receipts, and works wherever there is a data connection, 3G or Wi-Fi. The Messages app is intelligent, so it seamlessly defaults to iMessage when you send a message to another iOS user. It is very fast and well done, and should go far to convert the BlackBerry users who are addicted to their precious BlackBerry Messenger.
The iPhone 4S also supports standard SMS and MMS messages within the Messages app, but it does not have support for any instant messaging clients out of the box. The Facetime video calling feature that debuted on the iPhone 4 is present and accounted for, and I still think it is one of the best and easiest-to-use implementations of video calling to date, if actually making video calls is your thing.
iOS 5 has a built-in email client that supports Exchange, IMAP, and POP3 email accounts. It has support for multiple accounts as well as multiple message management and conversation threading. You can pinch-to-zoom to get a closer look at messages, and images and formatted text are presented without issue. It does not carry support for IMAP IDLE, so IMAP accounts do not get the benefit of push email services, which is something that I would like to see Apple add in the future.
Apple has been credited with the proliferation of the modern app store for mobile devices, and at this point the iTunes App Store offers nearly 500,000 apps for the iPhone 4S and other iOS devices. Though the iPhone 4S doesn't come with many apps installed out of the box, you can find countless applications both free and paid a few taps away. The advantage of this is the iPhone 4S is not bogged down with carrier-specific apps, unlike other platforms that suffer from a plague of carrier crapware.
One of the built-in apps that is new to iOS 5 is Reminders, a simple to-do app that supports multiple lists and sharing with other users. The interesting part of it is how it's been integrated with Siri. A command to Siri to remind me to check the mail when I get home will put a note in the Reminders app for just that. Since Reminders has the ability to access my location, as soon as I pull into my driveway, I get a ping on my phone to check the mail. Reminders can also be used for recurring events, such as notices to pay the rent. It is not the best option for power users who love to micro-manage their task list (there are already plenty of options in the iTunes App Store for those needs), but it is a slick and simplified to-do list for the average user.
Apple claims that the browser on the iPhone 4S is twice as fast as the iPhone 4, and side-by-side comparisons show that it is a few ticks faster when loading web pages. In real-world use, the iPhone 4S browser provides an excellent experience, with fast-loading pages, slick scrolling, and buttery-smooth pinch-to-zoom. This seemingly effortless performance more than makes up for the smaller size of the 3.5-inch display. The infamous lack of Adobe Flash may be a hindrance for some, but in actual practice, I never once missed it. The iPhone 4S supports enough forms of embedded video codecs that I did not encounter a point where there was a video on a website that I couldn't watch because of the lack of Flash support. Those who regularly visit restaurant websites may have a different experience, as those are the only sites that I can think of that still are primarily Flash-based anymore.
New to iOS 5 is the Reader option in the Safari browser, which strips down web pages to just the text content and images, eliminating ads and the surrounding cruft to make an online article easier to digest. The Reader mode works well and is a nice touch if you read a lot of articles from the web. The Safari browser also (finally) brings better support for multiple tabs, so you can easily bounce between various sites without having to reload them each time.