Updated from 1:18 p.m. EDT

The bull case for

Apple

(AAPL) - Get Report

over the past year has been that booming sales of iPod music players will create a "halo effect" that will lead to higher demand for the company's Macintosh computers.

While Apple has seen an uptick in Macintosh sales in recent quarters, that momentum may be slowed by the recent announcement that it is

switching the processor at the heart of its computers from the PowerPC line produced by

IBM

(IBM) - Get Report

and

Freescale Semiconductor

(FSL)

to chips made by

Intel

(INTC) - Get Report

.

Although Apple offered valid reasons for the switch, it could lead customers to delay computer purchases or choose rival systems based on

Microsoft's

(MSFT) - Get Report

Windows operating system.

Even with a recent drop, Apple shares -- at 29 times earnings estimates for the current year -- still are trading at a premium to its PC rivals. This implies big growth expectations for the company and particularly its computer business, notes Darren Chervitz, research director for Jacob Asset Management, which is long Apple shares.

"Without the transition, it seemed like all the signs were pointing toward that market share growth," says Chervitz, adding that he wonders "if this was the best time" for Apple to move to Intel chips.

(An Apple representative said later Tuesday that the company "currently offers the best lineup of Macs in its history, and plans to introduce more PowerPC-based Macs in the coming quarters. We think customers will continue to see the superior performance and value of Macs.")

Analysts have generally praised Apple's decision to go with Intel. The move promises to lower Apple's costs, which helps its computer become more price-competitive with rival Windows-based systems. And the move should help the company produce faster and more competitive notebook computers, demand for which is outpacing desktop systems.

In his presentation earlier this month, Apple CEO Steve Jobs noted that the Macintosh platform already has been through two such transitions in the past, first in the mid-1990s, when the company moved to the PowerPC chips, and then about five years ago, when the company launched OS X, its first Unix-based operating system.

But what Jobs failed to note is that Apple lost customers and market share with each of those transitions. Indeed, since the early 1990s, Apple has seen its share of the PC market slip from more than 10% to about 2% in recent quarters. Analysts have blamed that fall in part on those big changes, which created compatibility issues similar to those that could arise with the move to Intel chips.

"That's part of Apple's DNA," says Roger Kay, a technology analyst at research firm IDC. "Apple has sheared away all the people who want compatibility. All the people who want compatibility are using" Windows-based computers running on Intel chips.

But the big hope for Apple investors has been that dominance in online music players would help staunch the decline in PC market share. The company sold $2.2 billion in iPods in the first six months of its current fiscal year, up from just $520 million in the same period a year earlier, and claims to hold some 76% of the market for digital music players.

The strategy does seem to be having some success. In the first six months of this fiscal year, Macintosh sales have grown 28% to $3.1 billion, a rate significantly faster than that of the broader PC market.

Although Apple has just a small portion of the overall PC market, Macintosh sales constitute the lion's share of total company revenue. Even a small shift in overall PC market share in Apple's favor could provide a big boost to earnings.

But the move to Intel-based computers could give consumers pause. A subset of PC purchasers always wants the latest and greatest devices and will avoid buying now if they know something better is just around the corner, says Van Baker, a consumer technology analyst at research firm Gartner. Apple's transition could well dampen sales for Macintoshes until the new Intel-based ones come out, Baker says.

"Any time anyone announces a new platform or a significant change, people are predisposed to wait and see," Baker says.

And consumers might not be the only ones delaying purchases. While business customers generally use Windows-based PCs, the Macintosh is strong in several industry niches, including the entertainment and education sectors. Corporations tend to be cautious about adopting new technology, notes IDC's Kay. Companies often will wait to adopt a product until long after it is introduced, to observe others' experience with it and to make sure the bugs are worked out.

Stahancyk, Gearing, Rackner & Kent, a Portland, Ore., law firm, uses Macintosh notebooks and desktops for its standard office equipment. Don Kruse, the firm's IT manager, says Apple's move to Intel chips won't affect his purchase decisions in situations in which the firm needs new equipment, such as for a new lawyer or to replace a faulty computer. However, Kruse says he likely will delay more discretionary purchases until after the Intel-based computers have been out for a while.

"I've heard a lot of experts say that people don't care about the processor inside," he says. "To be honest, I do care about the hardware. I am a little concerned about the change to Intel. I know all the things that could go wrong there."

Hamed Khorsand, president of BWS Financial, believes Kruse won't be the only enterprise customer delaying Macintosh purchases. As part of an informal survey, BWS has found that a number of corporate customers have put large computer purchases on hold following Apple's announcement.

"I think this will prevent any halo effect from taking place now," says Khorsand, who has no stake in Apple stock and whose firm does not do investment banking.

Still, not everyone's convinced the transition is going to dampen Mac sales. While enterprise customers such as Kruse may care about a computer's innards, many consumers do not, particularly those who may be attracted to the Mac because of the iPod.

"Anyone who is dumb enough to buy a computer because of the iPod is going to buy in the face of

a processor upgrade," says Duncan Stewart, a portfolio manager with Toronto-based Tera Capital who follows the technology industry but does not currently have a position in Apple.

And many analysts believe the move to Intel will be beneficial to Apple in the long term, regardless of the short-term consequences. With the PowerPC chips, Apple was continuously running into supply constraints, notes one buy-side analyst, who asked not to be named.

"For Apple to increase its market share, they needed to go to Intel," says the analyst, whose firm is not involved in Apple's stock.

But if Apple's halo shines brightly in the future because of the move, it may well dim in the near term.