The ChangeWave Alliance survey — conducted among 3,115 consumers between Feb. 2 and Feb. 9 — found that of those who expected to buy a computer in the next 90 days, the percentage who planned to buy an Apple laptop was up 2 points, to 30%.

This follows a January survey that recorded the second sharpest dip in planned Mac purchases since ChangeWave starting tracking Apple’s computers. The sharpest dip, reported last September, sparked a massive sell-off in Apple (AAPL) shares. See The survey that squashed Apple, Part 1 and Part 2.

ChangeWave research director Paul Carton notes that the January fall-off in Mac purchases predicted by his survey showed up, right on schedule, in the NPD data released one month later. See Report: Mac sales off 6% in January; iPod off 14%.

Meanwhile, things are not looking so good for the increasingly long-in-the-tooth iMac and Mac Pro lines. Planned purchases of Apple desktop computers, which had held steady in the January survey, fell a point in February, to 26%. A refresh of the iMac line, widely anticipated at January’s Macworld Expo and now expected sometime this quarter, could turn that around.

“I expect we’ll see Apple muddling through,” Carton told reporters in a conference call Wednesday afternoon. But he added that while Apple’s share of the pie may be growing slightly, the pie itself — that is, the percentage of consumers planning to buy any computer — has shrunk to the lowest level ever recorded in a ChangeWave survey: 6% for laptops and 4% for desktops. (In June, 2007, those numbers were 12% and 7%, respectively.)

Apple is holding up better than say, Dell (DELL), Carton suggests, because its customers continue to express satisfaction with their purchases, as indicated by the chart at right. More than 80% of Apple customers declared themselves to be “very satisfied” with their new computers.  Most of the manufacturers of comparably-priced PCs found themselves in the 50% to 55% range.

As for the broader economy, a slight bump in planned consumer spending recorded in ChangeWave’s January survey was completely wiped out in its most recent polling. Better than three-in-five U.S. respondents (61%) said they expect to spend less money over the next 90 days, a 4 point decline in one month. See the chart below:

When the red (spend less) and blue (spend more) lines crossed in January 2008, Carton declared that the U.S. economy was headed into a recession — a call that turned out to be right on the money.

From the ChangeWave Alliance Web site:

ChangeWave runs a proprietary research network of 20,000 highly qualified business, technology, and medical professionals — as well as early adopter consumers — who spend their everyday lives on the frontline of technological change. (link)