It’s from the latest quarterly ChangeWave survey — taken shortly after the June 9 unveiling of the Apple (AAPL) iPhone 3G — and it shows that among consumers planning to buy smartphones in the next 90 days, 56% plan to purchase iPhones, double the percentage who plan to buy RIM (RIMM) BlackBerries. (The less said about Palm’s (PALM) prospects the better.)

But a few caveats are in order, only some of them provided by ChangeWave’s Paul Carton in his report on the survey here.

First of all, as Carton points out, although the results are based on a sample of 3,567 consumers, the chart  represents only the views of the 10.5% — fewer than 375 people — who plan to make a purchase in the next 90 days. That 10.5%, however, is a record for the survey, up from 7.4% last month; interest in smartphones is clearly high these days.

What Carton doesn’t say is that those 375 consumers are hardly a representative sample of the buying public. According to its website,

ChangeWave runs a proprietary network of 15,000 highly qualified business, technology, and medical professionals referred to as the ChangeWave Alliance. Alliance members are credentialed experts in leading companies of select industries who spend their everyday lives working on the frontline of technological change. (link)

Professionals working on the frontline of technological change, one presumes, are more disposed both to choose a smartphone over a regular cellphone and to buy the latest gadget to hit the market.

Moreover, anyone who receives ChangeWave’s regular e-mails knows to take both their advice and their findings with a grain of salt. A recent “Urgent Alert,” entitled “Could July 7 Become the Next Black Monday?,” included this all-red, all-cap headline:

INVEST CORRECTLY NOW AND YOU’LL MAKE MILLIONS

MAKE THE WRONG MOVE AND YOU’LL LOSE A FORTUNE

Still, ChangeWave survey’s do offer regular snapshots into the views of a subset of users, and RIM should not take their results lightly. Among ChangeWave’s most useful findings are reports of customer satisfaction, in which the iPhone consistently shines. The latest results:

An extraordinary four-in-five iPhone owners (78%) report they’re Very Satisfied with their iPhone. RIM ranks second, with a highly respectable 54% of its customers saying they’re Very Satisfied. Palm (29%), while up a few points since our previous survey, still ranks near the bottom in terms of customer satisfaction. (link)