I don't commute to work, so I can't adequately test battery life in real world situations, or develop an understanding of whether these products will last a typical workday on a charge. Instead, I travel extensively, especially lately, and of course I move around locally, visiting restaurants, stores, and other establishments. So I do what I can do, with regards to the day-to-day experience of using whatever mobile device I'm testing.
I've read the stories about the iPhone 4S's supposed decreased battery life and that Apple is investigating the issue with some users. I've not experienced that issue. And while I've only had the handset for several days now, I can report that, generally speaking, iPhone 4S battery life is certainly on par with other phones I've used. It's no better and no worse.
What I'm more concerned with, from a day-to-day perspective, is how the iPhone 4S fares with the common tasks that I, my wife and friends, and many others wish to perform with a smart phone as we move about in the world. That is, aside from core functionality like making and receiving phone calls, accessing email and the web, and playing games, how well does the iPhone 4S perform as a mobile companion, helping you find and check-in the places that matter to you?
This is an area where Windows Phone generally excels, though as I noted in a recent editorial, Where Windows Phone Still Falls Short, that system's integrated experiences are also in some ways incomplete, so your mileage may vary. But Windows Phone offers an excellent Local Scout feature, for finding restaurants, stores, sights, and other things of interest nearby, integrated ways to check-in via Facebook or Twitter, super-simple photo sharing (also via Facebook and Twitter), and more.
How about the iPhone 4S?
From a sheer apps standpoint, it's no contest. Anything you want, and a couple of hundred thousand things you don't, are available via Apple's voluminous App Store. And in some cases, this can be a huge advantage. A photographer friend, for example, would put up with the so-so camera in her HTC Trophy if she could just get Instragram. A heavy user of Google services, like Google+, Picasa and Google Reader, will find the iPhone a much friendlier and well-supported platform than Windows Phone. And games? There are some great ones on Windows Phone. There are tons more--tons--on the iPhone.
Apps are a dual-edged sword, however. Sometimes, too much choice leads to a weird form of indecision, and whether it's finding apps in an online store stocked with hundreds of thousands of them, or on a device with screen after screen of apps and folders of apps, more can be less. Too, apps enforce an implicit responsibility on the user's part: You need to know which app to use in a given situation and you need to find and launch that app on your phone to get something done.
Here's how this can be problematic on the iPhone 4S. I use Facebook, not Google+, Twitter, or Foursquare, to share things when I'm out in the world. This means checking-in of course, but also sharing posts and photos, and messaging with people, via Facebook's email-like system or via live chats. All of this functionality is integrated directly into Windows Phone, no app required. (Though, as noted in the previously mentioned article, some of this is not as full-featured as I'd like.) None of it is built into the iPhone 4S's iOS 5.
So when I take a fun photo--which is still a few steps too many in iOS 5, despite improvements--right at the moment I'd like to share that pictures--which is "immediately"--I can't. On the iPhone 4S, there are options for sending the photo via email, MMS/iMessage, or Twitter--but not Facebook or any other services. On Windows Phone, you can share to multiple online services, immediately, including the one everyone actually uses, Facebook.

The iPhone 4S offers integrated sharing with some services, but not Facebook.
So you learn to use the Facebook app, conforming to the iPhone's way of doing things. And it's not just different, it's less efficient.
Here's the thing. For many people, the safety of the iPhone's sheer number of apps outweighs a little inefficiency. And while I'm not sure if this qualifies as ironic per se, it's interesting to me that the iPhone's number one advantage today is the same advantage that Windows had/has in the PC market: The safety of numbers. You chose Windows PCs because that's where the apps were. Now you choose an iPhone because that's where the apps are.
So people develop habits. They organize the iPhone's home screens as they wish, and it becomes theirs. And as they buy apps and other content, and become more and more familiar with the way this system works, they're less likely to ever consider another mobile platform. Who's thinking about making Switcher ads now, eh?
As for me, I can be trained as well as any lemming. I learned very early on that I need to use the Facebook app for sharing, so I put it right on my first home screen. (Well, mostly; I still try to share from the Camera app.) One can conduct Internet and Wikipedia searches from that "search" screen that's to the left of the first home screen, and that's useful once you figure it out. And you can search for nearby places--with searches like sushi--from the Maps app, and, with Siri, for many other things as well. (I'll discuss Siri further in my coming review.)

Hooray for (local) sushi!
And there is of course some integration on the iPhone 4S, thanks to advances in iOS 5. Every picture I take with the device's camera is automatically uploaded, and in full resolution--to the Photo Stream that's attached to my iCloud account. These photos are thus automatically downloaded to my PC as well. That's very useful.
And that camera. As noted previously, the iPhone 4S camera is the best smart phone camera I've used so far. And while I expect the Nokia Lumia 800 to give it a run for its money, the iPhone 4S is here in my pocket, now. That, combined with the iCloud photo auto-upload functionality, is reason enough for many to choose this device. Add in the apps selection and the other unique iPhone/iOS features and you have the makings of a slam dunk.
Put simply, the iPhone 4S is a great mobile companion, with an excellent camera, useful online services integration, the best apps selection anywhere, and a slate of functionality that is competitive with anything offered on Windows Phone, or Android for that matter. I get why people like the iPhone so much. And while I could quibble over technical issues, the simple fact remains that the iPhone 4S is an excellent smart phone. All you need to do is carry one around to find that out.