More than one quarter of AT&T’s iPhone customers and nearly half of Verizon’s existing smartphone customers are prepared to leave their current phones behind for Verizon’s iPhone.

That stunning conclusion from online research firm uSamp is raising eyebrows because of the shockingly high number of people willing to brave the elements (and the cost) to grab iPhone 4 on Verizon’s network, even if it means pitching their existing phone in the waste bin.

Smartphone-lovers will have that chance as customers queue up tonight for Verizon’s iPhone tomorrow.

uSamp surveyed more than 700 smartphone users, finding that 29 percent of AT&T customers who intend to switch to Verizon for the iPhone are willing to wait in line on Feb. 10 to get it. Among existing Verizon customers who plan to get the iPhone, 24 percent report a willingness to stand in line, too.  When weighted across customers willing to switch handsets, more than one-quarter of all current iPhone owners will end their contracts with AT&T sometime this year.

For young consumers, devotion to the iPhone is even more intense: among AT&T customers intending to switch, 35 percent of those ages 18-24 and 50 percent of those ages 25-34 are willing to wait in line on the Feb. 10 launch day.

For Verizon’s current BlackBerry and Android users who report plans to switch to the iPhone, 46 percent of those ages 18-24 and 34 percent of those ages 25-34 agree they will wait in line on day one.

uSamp’s research shows diverging reasons for the willingness to switch.  For current AT&T customers, displeasure with AT&T’s network is by far the most important reason.  Nearly half of all respondents planning to leave cite dropped calls, followed by complaints about coverage and customer service.

The most recent example of AT&T’s high-profile failures was a very unhappy Will.i.am, whose attempts to tweet messages during the Super Bowl were met with frustration at every turn.  It seems AT&T didn’t deliver a reliable signal inside the stadium in Dallas, ironic considering AT&T is headquartered in that city.

“Att crashed … ahhhh!!!! The worse [sic],” tweeted Will.i.am, who has more than 800,000 followers of his Twitter account. That was shortly followed with “At&t??? Wow…no service during halftime…unbelievable.”

For Verizon customers, the largest group planning to abandon their existing phones are Blackberry owners.  Nearly two-thirds of respondents are prepared to give up a phone that used to be known as a “Crackberry.”  Why?  It’s yesterday’s phone, according to many respondents prepared to move on.

Many Android owners are also prepared to switch to the iPhone, even if their existing phones are just months old. These customers originally craved the iPhone, but settled on an Android phone just to stay with Verizon.  Now that they can have both the phone and the carrier, they will.

uSamp even measured regional differences in the motivation to switch.  Southern Verizon customers are most eager for the iPhone (30 percent), Midwesterners the least (13 percent).  AT&T customers who consider that company’s service as worthwhile as a stale Triscuit are evenly spread from coast to coast, averaging around 28 percent of all customers surveyed.

Tomorrow’s introduction will be followed by the next generation of iPhones early this summer, so some are planning to wait before upgrading.

[flv width=”640″ height=”500″]http://www.phillipdampier.com/video/WTTG Washington ATT v Verizon iPhone 2-3-11.flv[/flv]

WTTG-TV in Washington, D.C. explores the differences between AT&T and Verizon iPhones with Mark Kellner, technology correspondent for the Washington Times.  (5 minutes)