GWT

GWT (Google Web Toolkit) is compatible with lombok.

Edit your proj-debug and proj-compile batch scripts to add the following VM arguments:

java -javaagent:lombok.jar=ECJ (rest of arguments)

Thanks to Stephen Haberman for figuring this out.

GWT plugin in Eclipse

To use the GWT plugin in eclipse together with Lombok:
Install lombok into eclipse as normal (start lombok.jar as an application).
Download the JDT variant that GWT uses. For GWT v2.8.2 you'll need org.eclipse.jdt.core 3.11.2; for the current GWT development snapshot, this is org.eclipse.jdt.core 3.13.50. For more versions, search for jar files matching 'org.eclipse.jdt.core-{VERSION}-CUSTOM-GWT-{date}.jar in the lib/eclipse section GWT's github page.
Configure the 'GWT/Compile' option in the eclipse GWT plugin; in the advanced section, add the following VM arguments:

-javaagent:/path/to/lombok.jar=ECJ
-Xbootclasspath/p:/path/to/lombok.jar:/path/to/org.eclipse.jdt.core_fromPreviousStep.jar

Where the colon should be replaced with a semicolon on windows.
GWT Dev Mode needs a similar configuration: In the VM arguments section ('Arguments' tab), add:

-javaagent:/path/to/lombok.jar=ECJ

and in the 'Classpath' tab, add both lombok.jar and the org.eclipse.jdt.core file you downloaded.

The above instructions are contributed by Stas via the forum. Let us know if they work, or if you run into issues. Thanks and have fun!