Yes we do. You have to add the generated sources output dir to your classpath for GWT to see them, and make sure GWT doesn't see the "original" source files (either by putting them "later" on the classpath, or better not at all).
Here's our project layout (dictated by both Maven and the lombok-maven-plugin):
src/main/java -> source code that does not make use of lombok's annotations
src/main/lombok -> source code that uses lombok annotations
target/generated-sources/delombok -> output folder where "delomboked" files are generated
We then make sure to include target/generated-sources/delombok in the classpath, but not src/main/lombok.