However, there are defections, as well as many developers who use and prefer NetBeans. Sun this week boasted of 4.5 million downloads for NetBeans since it was launched, with more than 1 million occurring over the last six months.

Bob Laferriere, vice president of engineering at Echelon 4 Corp., said he switched his group's development environment to NetBeans 4.0 from Eclipse 3.0 because NetBeans has a more intuitive interface, an integrated Ant build environment and productivity tools he prefers.

"We wanted something with a more native look and feel," Laferriere said.

Much of Laferriere's complaint was with the Eclipse plug-in architecture. "Eclipse doesn't come preconfigured for the way developers work," he said, noting that it was a hassle for him to have to search for the plug-ins he needed to build applications.

Yet Laferriere also said he thought the refactoring support and code wizards for Eclipse might be a "little better."

Sun's Cramer said that while NetBeans was "stagnant for a while," Version 4.0 was a big boost in functionality and "we're getting a lot of people to switch."

Indeed, Cramer said, NetBeans is "not just an IDE, absolutely not. We offer the same RCP environment as Eclipse."

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Jochen Krause, president of Innoopract Informationssysteme GmbH, of Karlsruhe, Germany, said his team used to use NetBeans before the company became an Eclipse member. "Our developers had a hard time adapting to Eclipse at first," he said. "Nowadays they would not even think about switching back."

Justin Shaffer, vice president and chief architect at MLB Advanced Media LP, the Internet and new media arm of Major League Baseball, and an end user Sun promoted at its JavaOne conference, said while his organization mandates the platform developers use, "such as Java and JES [Sun's Java Enterprise System], we're very flexible with our development team on the IDE end of things. And most of the team is using Eclipse by choice."

Shaffer said he had "no complaints at all" about Eclipse, but he said he'd like to see more collaborative development support in the platform.

Meanwhile, some developers tout NetBeans' support for scripting languages through the Coyote project, which supports Jython and Groovy. But, while crediting Sun for its scripting language support, Krause said Eclipse has similar functionality available via plug-ins.

And beyond differences in the platforms, the two leading companies have both been perceived as exploiting their position in the respective organizations. Sun has been accused of dominating the Java Community Process to its advantage, and the same has been said of IBM regarding Eclipse. But Eclipse members note that IBM spun Eclipse out into an independent organization, while the governance model for NetBeans "is Sun and a few vendors or Sun appointees," a developer said.

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"Eclipse is independent; NetBeans is Sun," said Thomas Murphy, an analyst with Gartner Inc.

However, despite the positioning, Mike Milinkovich, executive director of the Eclipse Foundation, said he does not view Eclipse as competing with NetBeans—at least not in the IDE space.

"Eclipse is not an IDE," Milinkovich said. "First of all we're a platform —if you want to talk about it in just a technical sense. But the second thing is we're an open-source community that's doing a whole pile of projects. We're up to 36 projects, three of which make up JDT [Java Development Tools]. So there are 33 other projects that have nothing to do with the Java IDE.

"So there are lots of things that are going on at Eclipse that go far and beyond any attempt to compare Eclipse to NetBeans. We're not going to get into any feature-to-feature comparison with NetBeans."

In fact, many say the recent success of Eclipse can be largely attributed to Milinkovich. BEA officials acknowledged that Milinkovich's outstretched hand helped bring them to the table.

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