The concept of a device which can turn into multiple forms has been a holy grail for handset makers for years: who wouldn't want a phone that could also power a laptop, or a desktop, or even a tablet? Unfortunately, previous gadgets that have attempted this, such as Motorola's Atrix HD and LapDock accessory, have suffered from the "next year" syndrome: The concept is great, but the execution may require a few technological advancements. Asus's Padfone X is the latest device to claim that legacy.

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The Asus Padfone X is actually two devices: first, it's a fairly standard high-end Android(s goog) smartphone. This device is very similar to the Samsung Galaxy S5 and the HTC One M8: It has a 5-inch 1080p display, a Qualcomm(s com) Snapdragon 800 chip with an Adreno 330 GPU, and the latest version of Android, KitKat.

But wait -- this phone's is a tablet of sorts, too. For tablet use, it docks with the included Asus Padfone Station, basically a dumb screen with an included battery. Slide the phone into a slot in the back, and you've got a tablet with a decent 9-inch, 1920 x 1200 display. Here's the kicker -- the Padfone Station comes with the handset for $199 with a two-year contract on AT&T. That's the selling point: buy this phone, and you'll also get a tablet for free.

Informed factor

While many people separate tablets and phones into different categories, they're actually made up of the largely the same components. Tablets and phones are a spectrum, not a binary. There really isn't any difference between the two besides screen size, or cellular capability, and as phones grow larger, those differences matter a lot less than they have in the past.

Another benefit of using a phone to power the tablet is the slate can access the broadband chip: Yes, you can make calls and texts on the Asus Padfone Station without a separate data plan. But I only made a call to test the function, not because it made any sense. After all, if you're using the Padfone as a tablet, your phone is right there.

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By bundling two screens with one mobile computer, not only does that save money by cutting down on components -- you don't need two camera modules, two processors, two broadband chips, etc... -- but it also means, according to Asus's marketing, that users gain more flexibility. I'm not so sure.

Bezel's advocate

Here's the main problem with the Asus Padfone: the hardware needed to allow the phone to plug into the tablet makes both devices much larger and bulkier than they would be otherwise. The Padfone Station, in particular, has fat 1-inch bezels that really make it look dated. Large bezels aren't necessarily bad -- a certain amount of space makes the device easier to handle -- but the Padfone bezels are simply too big.

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When using the Padfone in tablet mode, there's a lot of weight towards the center of the device when holding it in landscape. That's where the docking slot for the phone is. When the phone's in there, it makes the tablet feel a little bit like a game controller with a big battery in the middle. It also means that using the tablet in portrait mode is very awkward due to the weight being in the middle of the screen.

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That completely Padfone package isn't actually that heavy. With the phone plugged into the tablet, my review unit weighed 672 grams -- which is roughly the same as my iPad 3(s aapl);  a 2-year old tablet, albeit with a bigger screen. The phone itself is actually lighter than's Google's Nexus 5 or the HTC One M8. But there's something about the design that makes the device feel heavier than it actually is, whether it is in tablet mode or as a standalone phone.

The Padfone and the Padfone Station both feel really solid, a welcome benefit of Asus's constant experimentation with new device forms, but sometimes feeling like a brick isn't a good thing.

Software

Asus promises "seamless" transition between using it as a phone and using it a tablet. It calls this feature "Dynamic Display," and because only Asus has this type of dual device, the software is exclusive to the company. Here's what's supposed to happen: You're using an app on your phone, you plug it into the tablet, and suddenly the app is displayed on the tablet's lager, higher resolution screen.

Sometimes, the Padfone is weird. For instance, when in tablet mode, the standard Android screenshot keys don't work.

Sometimes, the Padfone X is weird. For instance, when in tablet mode, the standard Android screenshot keys don't work.

What actually happens is that most of the time you'll get an error message, especially if you're using an app that didn't come pre-installed on the device. The device provides two options, restart the app in Pad mode (which is recommended) or add the app into Dynamic Display list to keep running it without restarting in Pad Mode. Usually I just restarted in Pad Mode, because if you use Dynamic Display with an app that doesn't support it, when you plug in your phone, you'll just get taken to the tablet's home screen. This happened with both Google Now and Twitter, so it affects important apps. Pressing the icon to boot up an app again on the tablet isn't a dealbreaker, but it is disappointing.

There's a slight lag when plugging the phone into the tablet. While waiting, you'll get the circular hourglass icon Asus uses. Once, the pairing took at least 15 seconds, but usually it only takes a short time for the tablet to boot up. It's not quite instantaneous, but it's more than good enough, especially considering I was using a review unit, and the software isn't final.

The Padfone's version of Android, aside from the docking features, is fairly close to stock. There are a few aspects that could be improved, such as the cluttered stock keyboard, but the interface is snappy, and any current Android user will feel at home.

Battery

So if there's no guts inside the Padfone Station, what is there? Well, there's a huge 4990 mAh battery in there. This is handy, and is a major reason why someone would like to purchase the Padfone X over another Android phone in its price range. Instead of carrying a external battery pack around, you can simply carry your tablet. You do have to charge the Padfone Station and the Padfone separately though. If the Station is out of juice, the Padfone can't power it, but it does work the other way around.

Unfortunately, you may need to haul that battery-slash-tablet around: While I didn't run any specific battery tests, the Padfone X is not best-in-class. I felt the HTC One M8 has superior battery life, and I was often reaching for my charger well before the end of the day.

The biggest new feature is the price

The Padfone as a phone is solid. The Padfone as a tablet is an oddly weighted, middle-of-the-road device. But the concept works: The tablet is perfectly usable and the phone can do everything you'd expect from a modern smartphone. Together, for the price of a high-end phone by itself, it could certainly gain a following.

The Padfone X is the third device in Asus' Padfone line, and while I haven't used its predecessors, I can guess that small improvements and spec bumps make the Padfone X better than last year's version. But the key to the new Padfone is the price: the Padfone 2 cost $800 when it launched, making it more expensive than other high-end handsets. But the Padfone X only costs $600, or $199 with a 2-year contract, bringing it into the same bracket as the iPhone and the Galaxy S5.

While I would love to see next year's Padfone get slimmer, faster, and have less bezel, I think the most important thing is for the price to keep falling. After all, the extra hardware needed to physically dock the device will prevent the tablet from ever being the leader in skinniness. It's hard to imagine the Padfone line competing with HTC or Apple in terms of premium feel. That's why its unique form makes sense as a mid-range device, where the value proposition of a tablet-plus-phone becomes the most compelling, and the added bulk becomes less of a deal breaker.