Under normal circumstances, I would not be considered a target customer for the iPhone 4S. I bought the iPhone 4 on launch day. I was not up for renewal until late November.
Because of work commitments (look for the upcoming "Taking Your iPhone 4S to the Max" co-written with fellow TUAW bloggers), I paid the early upgrade penalty and received my iPhone 4S on October 14.
I've now spent 10 focused days with the iPhone 4S, exploring onboard features for technical coverage (I probably know a little more about how to make selections and share media in the Photo app than any normal person ought). The rest of the time I've been doing what the iPhone is meant to do: place phone calls, run errands, take family pictures and so forth.
Here's some extremely subjective feedback on my personal 4S experience during this time.
I know there's been talk about the decreased standby battery time, but man does this iPhone rock out battery-wise. My daughter and I took a trip over the weekend, and she subjected my phone (and my grandfathered unlimited data plan -- bless it) to an unmentionable number of hours of "My Little Pony," courtesy of YouTube.
The iPhone 4S also endured several games of Bejeweled (normally a battery sucker), navigation through maps, and lots and lots of Siri. Despite near constant use, the iPhone 4S made it to the end of each day. It's noticeably a usage power-house compared to the iPhone 4.
The shutter speed on this unit is simply amazing. With Autumn on full-blast, the child and I spent a lot of time throwing leaves into the air and snapping pictures of them as they fell. We have picture after picture of those leaves frozen in the air, frozen in time, with beautiful crisp resolution. You could not do that with earlier generation units.
Whether it's finding a restaurant, setting an alarm, or updating a to-do list, Siri has seen lots of use over the last 10 days. It already feels natural to pick up the iPhone, press the Home button and speak.
Siri, in and of itself, has been the main reason I am currently not using a lock code on my phone. That instant access is just so seductive. "Read me my texts" and "Reply to it" are so simple to use and the voice recognition component is absolutely insanely good. I used Voice Memos a lot on my old iPhone -- including the whole unlock / find the app / tap it / start recording sequence. I've touched it maybe once since the 4S arrived.
To be fair, my wish list for Siri is now about a mile long (launching apps is near the top) and the technology is far from perfect, but the feature is amazing.
The built-in mirroring got reasonable use this past week as I ended up demoing my 4S a lot. The feature works exactly as advertised, with good mirrored responsiveness. If you demo the iPhone, it's a must-have option -- one that you don't get on any other device but the iPad 2.
The iPhone 4S feels plenty zippy, though I should note that I haven't subjected it to serious testing just yet, as I've been focused on writing. This means I haven't done any hardcore gaming, either.
It's not all roses, of course. I'm annoyed by mobile Safari's lack of responsiveness to typing URLs (this seems to be an iOS 5 issue and not unique to the 4S) despite the 4S's high-end processor. I know the extra power is there, I just haven't really internalized it through any personal experience of performance gains.
I have run signal strength tests on the 4S, put it in my signal-killing hands, and made phone call after phone call. Both objectively and subjectively, this is a far better phone-call making unit than the 4 ever was. It maintains good signal quality under more stress, and does not seem to suffer from my hand-held attenuation the way the 4 did. I'm not a quality assessment professional for telephony, but my 4S just seems to work better. I like it a lot.
If you're an iPhone 4 owner, should you consider a jump to the 4S? Each of the points I've listed above may be a motivator. If you need that better camera, that better battery, or Airplay mirroring, the 4S has those items in spades. If you want Siri or the upgraded processor, you're not going to find those anywhere else. If you've had signal problems in the past, the 4S holds out the promise of better telephony, at least in my non-scientific experience.
I'm really happy with my 4S purchase, even more than I expected to be. Yes, it has the same case shape, but as far as I can tell it feels like a new generation -- not just a speed bump. I wish the Apple paradigm (new models each year) and the carrier paradigm (subsidized items, two year contracts, early cancellation penalties) were more in sync.
Depending where you are on your contract, the upgrade may or may not make sense financially. In terms of equipment quality, however, I think most people will be satisfied customers once they really start using the 4S.