With all this said I definitely would LOVE to see Eclipse RCP integration on top of Spring, leveraging existing complimentary libraries of spring rich (such as the data binding stuff). But I wouldn't want to force spring rich users to HAVE to use eclipse's platform: in many cases it's just not necessary (particularly when a team already knows Swing, cares about platform independence, and doesn't want the complexity of the eclipse plugin model - yet another thing to configure...)
But I guess we start to talk about unlayed eggs. We need an extense prototype or something real. You know, I guess you Spring RCP guys may provide a client demonstrating/integrating most of the of Spring RCP features, you think are horse-crazy (aka best). And then we Eclipse RCP maniacs will try to convert it using Eclipse. When this is done, we can see where to cut things and split the Spring RCP api. You know there should be something like a core-api and some special-apis for integrating it into either the Eclipse or Swing world.
Or maybe the Spring RCP project may be split up into two projects targeting the diffrent platforms by not sharing code but sharing ideas, possibilities and so on.
So the question is, is the Petclinic example that kind of comprehensive?
Maybe we should wait for a main release of the Spring RCP project before doing further talks. Sometimes things must grow a bit more to talk about. But sadly I am not the right person to judge the matureness of the Spring RCP project.