As usual, Apple (NASDAQ:AAPL) CEO Tim Cook used his opening keynote at the Worldwide Developers Conference this week to unleash a host of metrics painting the Cupertino-based tech giant as the good guy. While Cook is understandably biased, metrics are tough to twist -- especially the particular figures he emphasized during the event. In fact, three particular metrics were powerful enough to reinforce the bull case for long-term Apple investors. Here are the three most convincing numbers Cook shared.

Image source: Screenshot from recording of Apple's WWDC 2014 Keynote.

130 million
That's the number of customers who bought an iOS device in the past year who were purchasing their very first Apple device, Cook asserted. To give that number greater meaning, consider that Apple has sold over 800 million iOS devices since the operating system was first introduced. For a more recent comparison, in the past 12 months Apple sold 230 million iPhones and iPads combined. Even including iPod Touch sales, more than half of Apple's new iOS customers in that yearlong time period were buying their very first Apple product.

Nearly 50%
China doesn't need much of an introduction as an important market for Apple. Not only is it globally the No. 1 smartphone market, but it's also one of Apple's best long-term growth opportunities, especially with the world's largest carrier finally selling iPhones as of January of this year.

So how is Apple doing at attracting new customers in the important market? Nearly half of iPhone buyers in China in the past six months switched from Google's Android to iPhone, Cook said.

As any longtime Apple shareholder understands, the company's best side is found in customer retention. While Apple is clearly successful at acquiring new customers, it is unmatched when it comes to keeping them. A tightly integrated ecosystem of products, software, and services means that the value of a new Apple customer goes far beyond the initial margin contribution that can be attributed to the first sale to that person.

Image source: Screenshot from recording of Apple's WWDC 2014 Keynote.

Citing a recent report by ChangeWave Research, Cook said iOS 7 has a customer satisfaction rating of 97%, a figure high enough to lead to a host of follow-up sales of other products and future iPhone upgrades.

For long-term investors only
For the traders who like to serve up Uncle Sam massive short-term gain tax payments at the end of the year, these numbers probably won't mean much. Even for the Street and its handful of emotional price-target-swinging analysts, these figures may be of little value. But for the Foolish investors who dare to buy excellent companies and hold for the long haul, Apple is clearly still on its A game.

With no sign of deteriorating pricing power and an ecosystem as robust as ever, Apple's unparalleled high-end user experience approach looks poised to continue raking in loads of cash. This reliable stream of cash flow and shareholder-friendly policies for returning cash to investors make Apple stock an excellent value even at $645 per share. These three figures are a nice reminder, for buy-and-hold Apple investors, that Steve Jobs built an enduring business.

Daniel Sparks owns shares of Apple. The Motley Fool recommends, Apple, Google (A shares), and Google (C shares). The Motley Fool owns shares of, Apple, Google (A shares), and Google (C shares). Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.