Today I tried to run the Apache Wink on the Google App Engine. It worked quite seamlessly. I only needed to add a slf4j-jdk14 bridge for logging and it just worked.
The only disappointment is about the lack of support of JAXB by the Google App Engine.
JAXB is used quite widely by the Apache Wink and is required by the JAX-RS (JSR-311) spec. We have based some of important functionality on JAXB: for example Atom and Json support is based on JAXB. So these providers won't work. But everything else I tried till now, works quite fine.