The new iPhone 4S is here—though you might not know it at first glance. Like the transition from the iPhone 3G to 3GS in 2009, the change from iPhone 4 to 4S is not a cosmetic one. Apple seems to be making a habit of alternating between major cosmetic changes and major internal changes when it comes to iPhone hardware, and this is definitely an "internal change" kind of year. But it's what's inside that counts, right?

The iPhone 4S is now the only device that comes with what Apple describes as a voice-activated virtual personal assistant called Siri. The iPhone 4S also sports a completely redesigned antenna that Apple claims will drastically improve call quality and data speeds over the iPhone 4. And the iPhone 4S comes with the new A5 processor introduced in the iPad 2 earlier this year, giving it a performance boost over its predecessor. Even the built-in camera received some nice spec bumps.

These are the most important new elements of the iPhone 4S, and they're what we'll focus on in this review. If you want to read more about the basic iPhone 4 design, you can read our in-depth review from 2010. And if you want to learn all about the new features that come with iOS 5—which works on a variety of Apple hardware—we have a review for that, too! But right now, it's time to focus on the major new features of the iPhone 4S.

"Are you there, Siri? It's me, Jacqui."

Now that the iPhone 4S has been out for a few days, the big question we've been getting is: how good is Siri, really?

Don't know Siri? Apple introduced the technology along with the iPhone 4S this fall and billed it as a "virtual intelligent assistant." To quote myself after Siri's introduction:

"Siri offers iPhone 4S users a way to interact with their devices, apps, and data with natural language voice commands. Users can send and receive texts or e-mails simply by talking to Siri, find out whether there will be rain today, create new Reminders and calendar items, ask for directions, move appointments, and more. Not only that, but users can ask Siri to look up a plethora of information, such as restaurant reviews from Yelp or even simple facts from Wikipedia or Wolfram Alpha. Cooking and need to convert a recipe's tablespoons to teaspoons? Ask Siri and get the answer back almost instantly without having to type a single character."

Apple's claims were bold, and the press demo at Apple's campus was even bolder. It was difficult to believe that Siri could be able to accept natural language input and parse context so easily. This wasn't like other phones, which require the user to adhere to a strict list of pre-determined commands and bark them at the appropriate times—Siri claimed to listen as if it were a person, able to understand the meaning behind your words without requiring you to be explicit. And it could perform so many tasks!

Reading the first round of early reviews, you might come away thinking that Apple found some way to shrink Mad Men's Joan Holloway and pop her into a computer chip. Though Siri shows real potential, these kinds of high expectations are bound to be disappointed. Apple makes clear that the product is still in beta—an appropriate label, in our opinion.

Certainly, we had moments during our testing when we laughed at Siri's clever ability to decipher our casual language and not only deliver a result, but a very specific and accurate result.

A query about how many calories were in a tortilla provided the answer plus a whole host of other nutritional information. A query about how to find a small neighborhood market switched over to the Maps app and showed me directions between the market and my current location. When asked where one of my friends was (we were meeting up at a certain time and he was late), Siri looked up that friend in Find My Friends before showing me a map of his current location.

In the kitchen, I can have Siri set multiple timers for different elements of a recipe without having to wash and dry my hands (as long as I have a pinky finger free to hold down the Home button, that is). And one of my favorite activities for Siri is creating reminders. Telling Siri to "remind me to call Apple PR tomorrow at 10am" is far faster and easier than manually entering that info by hand into the Reminders app.

When given direct and clear tasks, Siri performs well, and it's nice not having to memorize a strict list of commands.

But for as many times as we came away impressed, we had an equal number of serious ELIZA moments. These mostly came when we got more casual with Siri. As Apple suggests, we began breaking away from our stiffer commands ("call Leah") to Siri and speaking to it (her?) as if she were a real person—only to be ripped out of the fantasy by something that Siri has so badly misinterpreted that it's easier to just think, "I'll do it myself."

For example, I might say to Siri, "Send a text to Jason, Clint, Sam, and Lee saying we're having dinner at Silver Cloud." You can theoretically send texts to multiple people with Siri, which is why I was trying out this feature. A typical response from Siri would be a message to Jason only, with the text reading something like, "Clint Sam and Lee saying we're having dinner at Silver Cloud."

This message doesn't make sense, and it's not going to the right people. So I could then say to Siri, "Edit message to say: we're at Silver Cloud and you should come find us." At this point, a classic Siri response would be to amend my text, so now it says, "Clint Sam and Lee saying we're having dinner at Silver Cloud to say we're at Silver Cloud and you should come find us." Then, I might try to fix the list of people who receive the text, but Siri won't want to send it to Sam and Lee, she'll want to send it to "Sam Andlee," who doesn't exist in my address book. At which point I have my "screw it, I'll do it myself" moment.

After having enough of these experiences, I do have a few pro-tips for speaking to Siri. (Also, let's just hope you don't have any friends named "Cesar," because Siri seems to really want to interpret that as "sister" about 80 percent of the time.) When Siri asks you verbally if this task, text, reminder, or note is correct while presenting buttons to confirm or cancel, it doesn't seem to like answers like "yeah" or "yep." This may simply be because of how we're speaking, but Siri just didn't behave well when we answered that way.

Also, don't try to get cute with Siri—starting out every statement with "Siri, can you…" not only gets old for the people who have to listen to you constantly talking to your iPhone, it also seems to add unnecessary complication to your request. Siri can parse less-than-efficient wording at a decent level, but you increase your chances of getting an accurate result if you treat your commands like your English teacher always said: eliminate unnecessary words!

And it's a given that a quiet room will get you better results than a loud and busy one, though we had better-than-expected luck with Siri in places like bars and office environments. (This isn't to say Siri performed well in those scenarios—some of my friends openly joked about Siri's accuracy after getting a loud bar demo—but it performed better than we thought it would.)

The best part about Siri is the fact that you can (or should be able to, anyway) speak to it like you would speak to a person without having to conform to a special speaking syntax—the number one turn-off for "regular" people using voice control features. To say that Siri is already there would be disingenuous, though. It needs some work, but the groundwork has been laid to make Siri a powerful and more efficient way to interact with your devices. Even with my share of ELIZA moments, I still found that using Siri to look up information was generally faster than finding the appropriate app and typing in my query by hand (and I'm a fast iPhone typer). We don't know when Siri will be out of beta, but we'll be there to put Siri through her paces again when she's ready.