Are Apple’s lawyers getting ready to go on vacation? For the second time in as many days, the company has agreed to settle a lingering class action suit.

On Thursday, it was a pair of complaints out of Canada that 1st, 2nd and 3rd generation iPods were delivering something like three hours of music, not eight hours as advertised. Although one case was granted class action status and the other wasn’t, Apple (AAPL) agreed to settle both, according to the Montreal Gazette, offering $44 store credit to any Canadian who purchased one of the affected iPods before June 24, 2004. As many as 80,000 could be eligible. Hearings are set for May 26 in Montreal and June 20 in Toronto.

Then on Friday, according to the LA Times, Apple agreed to pay some 2.3 million Mac owners refunds of $25 to $79 to resolve claims that some of its power supplies were prone to fray and spark and self-destruct. Customers who bought replacement adaptors for PowerBooks and iBooks could be eligible for the refunds, according to documents filed in federal court in San Jose. A final court hearing is scheduled for Sept. 8.

Still pending, notes the Gazette, is the case filed against Apple Canada last fall by law student David Bitton who was surprised to discover that his 8GB iPod Nano held only 7.45GB. According to his lawyer, Bitton is asking for the full $220 purchase price, but will settle for 7.5%, plus court costs.

Drilling down into Apple’s (AAPL) recent string of boffo quarterly reports, analyst Toni Sacconaghi Jr. of Bernstein Research finds both strength and vulnerability in Steve Jobs’ relentless pursuit of high-margin computer sales.

In his second report since Bernstein initiated coverage of Apple (see here for the first one), Sacconaghi notes that:

• Apple’s global PC market share has increased in 10 of the last 11 quarters,
• unit sales have grown 28% or better in each of the last four quarters
• U.S. notebook sales have been particularly strong, accounting for 47% of Apple’s Mac unit growth and 52% of its revenue in Apple’s most recent quarterly report.

But amid all that good news, he sees risks ahead for Apple investors. It’s tempting, he says, to look at Apple’s slim 3% slice of the global market for PCs and assume that Jobs can easily grow his Mac business at least two fold in the next five years or so — an assumption that helps explain the high multiples in Apple’s current share price.

But if you look at the high-priced markets Apple chooses to play in, says Sacconaghi, you see that it already has a surprisingly dominant market share — without much room for growth.

Take, for example, the market for the most expensive notebook computers. Dividing notebook price ranges into fifths, or quintiles as the statisticians call them, Apple already has a 29% share of the U.S. market for notebook computers in the highest quintile — up “stunningly,” notes Sacconaghi, from 8% three years ago. In the consumer and education market (i.e. excluding business computers), Apple share of the top quintile notebook market is nearly 46%.

While other PC makers have been lowering their average selling price, Apple has been steadily increasing its price premiums relative to the rest of the market — great for keeping profit margins high, but not so good for growing market share.

“Accordingly,” Sacconaghi concludes, “we believe Apple faces a trade-off in its Mac business over the next 2 - 3 years: either lower price (and margin percentage) to sustain share gains, or retain its current price premiums and face slowing unit growth.”

Below the fold, a graph from the Bernstein report showing the rapid growth in Apple’s share of the premium notebook market from 2000 to today.