Wall Street seems to think that the Cupertino company, once an also-ran in the shadow of Microsoft (MSFT) and its band of PC makers, is the tech growth story of the moment.

But will it last?

Here are some factors investors should consider as they ponder how much room Apple has left to run.

PCs

Apple’s update of the iMac product line this week shows that company is still serious about trying to make money off of desktop computers. But the iMacs, which start at $1,200, aren’t exactly aimed at the mass market; as Intel (INTC) and Advanced Micro Devices (AMD) pointed out in their recent earnings calls, consumers are clamoring for cheaper PCs, making it tougher for industry players to eke out decent profits.

Will Apple’s growth come from desktops? Odds are, no. Laptop sales are growing much faster, particularly among the sophisticated consumers Apple is courting. If Apple can grab market share through laptop sales in the second half of the year, it will be an encouraging sign. Of note: The company is amping up its distribution through Best Buy (BBY) stores, so that should have a positive impact this holiday season.

iPods

Much has been made lately of the fact that Apple’s iPod revenue growth is slowing. (Few cared to listen when I pointed this out months ago, but no hard feelings.) Does this mean the iPod business is in trouble? Not at all – Apple still dominates in music players. It might, however, mean that investors can’t count on iPods to fuel much of Apple’s future growth.

Apple hasn’t gotten the bump many expected from video iPod sales – probably because consumers feel the video downloading experience is crummy, and unlike the deal with CDs, you can’t easily rip movies onto a computer and transfer them to an iPod. How could Apple get growth moving in iPods again? Take the iPhone design, strip out the phone, add video recording capabilities, and call it an “iPod camcorder.” I’d pay a few hundred for one, no question. Will Apple do it? The jury’s out on that one.

iPhone

For now, then, all eyes are on the iPhone. So far it’s had an amazing run; it sold 270,000 units in the first 30 hours, and Apple executives still seem confident that they will sell 1 million by the end of September. One of the remarkable things about the iPhone launch is that Apple got so much right the first time – the conventional wisdom in the mobile industry is that a first phone effort turns out messy. But Apple had lots of experience perfecting wireless devices because of its history with WiFi in Macs, and that proved useful in phones as well.

Will the iPhone’s run continue? Much depends on the reception Apple gets in Europe and Asia as it expands to those markets. On the plus side, consumers there are already used to paying top-dollar for the best phones – so price won’t be as much of an issue. On the minus side, there are fewer affluent buyers in many markets, and Apple’s brand isn’t as strong in some countries as it is in the U.S. (though it’s pretty darn strong everywhere). Among the things that will help Apple are the iPhone’s software-powered interface, which can be modified for language and culture considerations, and its ties to companies like Google (GOOG), which are quickly growing overseas. If iPhone sales do take off, look for Apple to use that as a Trojan Horse to sell Macs into new markets. (In the U.S., Apple used iTunes to manage iPhones.)

If the company figures out how to use a successful iPhone to sell more Macs into overseas markets, that growth question will take care of itself.