"There's always risk, and I think the biggest risk is you've got infrastructure that is being run -- something strategic for you as a company -- that's being run by someone else," said Hilwa. Google's interest in the service might change over time, Hilwa said.
App Engine is hosted on the same infrastructure as Google's own applications. The only language supported on App Engine currently is Python, but the company is set to expand to other languages, Koomen said. "We think [Python is] a very natural language to write Web apps in," said Koomen.
Google cites competitors like Amazon Elastic Compute Cloud service but said the differentiator is App Engine's focus on Web development. "It's a platform aimed specifically at making Web development easier," Koomen said.
Developers have the option of using Google's AdSense service, an advertising platform for Web publishers.
Version 1.5 includes Java 5 language capabilities, including Java 5 syntax support. Java generics, enumerated types, annotations, auto-boxing, and variable parameter lists are enabled as part of Java 5 backing.
Also, the compiler in version 1.5 produces faster code. This is done by performing deep inlining, better dead code elimination, and other forms of enhanced static analysis, Google said.
GWT features libraries to build AJAX, including reusable libraries for implementing user interfaces, data structures, client/server communication, internationalization, and accessibility.