It's been more than eight months since Steve Jobs passed away. Along with sadness over Jobs' passing, Apple (NAS: AAPL) investors the world over were concerned that this would mean the end to Apple's greatness.

Yet in that time, the stock is up 54%, the company has produced stellar quarterly results, and it's instituted a new dividend.

But the ride is far from over. If you've been sitting on the sidelines because you think you've missed the action, now is the time to make your move. Here are three reasons why.

The stock is dirt cheap
There are lots of metrics I could focus on here, but I think the following graph captures it all. Usually, when a company's stock price rises, it's a combination of two factors: increases in both earnings and the multiple (P/E) investors are willing to pay for the company.

With Apple, this isn't the case. Apple's stock price has continued upward in spite of the contraction of its P/E. This, of course, means earnings have gone through the roof.

AAPL data by YCharts

As it is, Apple trades for just 14 times earnings. If you back out the company's $110 billion cash hoard, that shrinks down to just 11 times earnings.

At these rates, investors believe that Apple will be growing by only about 10% to 15% in the future. In reality, that would represent a huge slowdown, as earnings have grown 58% per year for the past five years.

I understand some investors are worried that there's a cap on how big Apple could become, but last time I checked, Nasdaq didn't have a limit on a company's size.

Rapid adoption
Taking a stroll down a city street, you could be forgiven for thinking that everyone in the world already owns an iPhone or iPad. The reality, however, is a bit different.

Smartphones reached only 50% penetration in the U.S. this year, and internationally, only 10% of global citizens have the devices.

In the United States, it's a two-horse race between Apple and Google's (NAS: GOOG) Android operating system, but there's still a ton of market share to capture globally -- where Google is handily in the lead.

Source: IDC.

Though BlackBerry might have a dubious future, competition will surely exist from Microsoft as well. But global conversion to smartphones and any incremental market-share capture will mean big business for Apple, which is already one of the most popular brands in China.

Of equal importance, the adoption rate of tablets is on pace to break historical speed records.

Source: Technology Review.

Source: Technology Review.

This means that though the iPad accounted for only 17% of Apple revenues last quarter, this number could easily balloon in the coming years.

But really, it's not about the hardware
When we think of Apple, the iProducts are obviously the first things that come to mind. But famed investor David Einhorn sees it differently, and I agree with him. In an industry that is ripe for disruption and changes rapidly, any sustainable competitive advantage is a big deal -- and Apple's operating systems provide that advantage.

Think of it this way: For the past five years, my wife owned a Hewlett-Packard (NYS: HPQ) laptop. During the time she owned it, she purchased an iPod and an iPhone. When it came time to get a new laptop, there was no question that it would be a Mac. She wanted her devices to communicate and sync with one another -- and that was only possible if she had a Mac.

As hedge fund manager David Einhorn pointed out: "Once the user has a second device, [Apple] has captured the customer. At that point, a future competitor has to make a product that isn't just a little better, but a lot better to get people to switch."

This is the most underappreciated aspect of Apple's model. Something as cheap as an iPod could be the gateway drug that leads international consumers to becoming full-fledged Apple buyers.

This isn't empty pandering
I've backed up my personal sentiments about Apple in both word and deed. I've made a bullish CAPScall for Apple on my All-Star profile, and the company currently accounts for 8.6% of my personal portfolio.

If these numbers have impressed upon you the huge opportunity in the mobile computing space, I suggest you check out our latest special free report: The Next Trillion-Dollar Revolution. Inside, you'll get the name of a chipmaker whose devices will be in millions of the new devices Apple is selling. Get your copy of the report today, absolutely free!

The article 3 Reasons You Should Stop Sitting on the Sidelines and Buy Apple originally appeared on Fool.com.

Fool contributorBrian Stoffelowns shares of Apple and Google. You can follow him on Twitter, where he goes by@TMFStoffel.The Motley Fool owns shares of Microsoft, Google, and Apple.Motley Fool newsletter serviceshave recommended buying shares of Apple, Microsoft, and Google and creating bull call spread positions in Apple and Microsoft. The Motley Fool has adisclosure policy. We Fools don't all hold the same opinions, but we all believe thatconsidering a diverse range of insightsmakes us better investors. Try any of our Foolish newsletter servicesfree for 30 days.

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