Since the iPad's introduction in 2010, there's been a promise in the air: that we could finally stop lugging around laptops in favor of these lightweight, totally mobile touchscreen devices. The next year, everyone rushed to make their own versions of the iPad, and the promise got bigger.

So people bought them. In 2013, Pew Research's Internet Project found that one-third of all Americans owned tablet computers. But four years later, consumers are still waiting for that promise.

Sure, we use our tablets for lots of things: browsing, watching video, reading and gaming. But when it comes to replacing the laptop? Tablets still have their limitations.

Meanwhile, the market for tablets is slowing, according to analysts. In its latest assessment of the tablet market, the International Data Corporation found that the tablet market is now growing in the single-digits, as many consumers are asking the question that dogged the iPad's early days -- what, really, are we supposed to use a tablet for? And what's the future of the tablet?

Tech giants looking at this space have very different answers to that question. With the introduction of the Surface Pro 3, a 12-inch tablet designed specifically to replace a laptop, it's clear that Microsoft thinks that the future of the tablet market depends on morphing high-end tablets, physically, into featherweight laptops.

In a Tuesday presentation, Microsoft's Panos Panay, a company corporate vice president in charge of the Surface, noted that his audience of journalists and analysts were almost all packing laptops -- in most cases, some version of Apple's MacBook Air.

"What happened?" Panay asked at the event, as the camera on the live Web stream panned out to show a crowd with laptops in tow and a slide popped up on-stage claiming 96 percent of iPad users also own a laptop.

"They're designed for you to sit back and watch movies; they're designed to read books," he said. "They're made for browsing the Web, snacking on apps."

Laptops, he said, are designed the way they are because you "actually need to do things."

But that's not how everyone is looking at it. Certainly not Apple, which poked fun at the Surface -- a device that works best with its additional keyboard cover accessory -- in a keynote last October.

"They chased after netbooks," said Apple chief executive Tim Cook, in front of a slide showing a road sign with a wildly squiggling road. "Now they're trying to make PCs into tablets and tablets into PCs. ... We have a very clear direction and very ambitious goals."

The Apple view, based on the company's latest moves, is that the programs that people use should be adapted to fit the tablet -- not the other way around. In the Apple universe, software is changing to adapt to the new hardware. In fact, many expect that Apple is going to show off re-imagined, touch-optimized versions of some of its traditional computer programs such as TextEdit and Preview, as 9 to 5 Mac reported. Apple has already given that kind of treatment to other core programs that seemed like they needed a full computer to run, such as Garage Band, iPhoto or iMovie.

The truth is that, in both cases, the companies are asking consumers to give up on something. In Apple's case, it's a little bit of performance and usability while the touch-interfaces get worked out. For Microsoft, it's asking for a little more leeway on making things sleek -- 12 inches is a big tablet, after all --  in order to provide requisite power and productivity.

In other words, tablets are still in a period of betwixt and between, and we'll probably be dealing with growing pains for a while yet.