Just some further comments on DataSet. I haven't really spoken to all involved but my understanding of the history of DataSet is that it was developed as a poor man's substitute for people who didn't need a heavy weight ORM solution, e.g. trying to avoid EJBs and even hibernate. So, it was designed to be simple rather than feature rich. If you wanted something feature rich, go use hibernate (or your favourite alternative). Given these original intentions, DataSet does a reasonable job but does have some limitations.
Now, time has moved on and we have nosql and LINQ-style options available in the various languages. Groovy certainly has some wonderful options available to it courtesy of its Java heritage. However, if Groovy wants to compete with other languages, I think it needs some additional value add over the top of the Java options. I think this is certainly doable but I am not sure that DataSet (at least in its current form) will be the right way forward in the longer term. It certainly makes sense to tweak DataSet when we find obvious short-comings that can be easily fixed but for major changes I am wondering whether starting from scratch with a new offering taking into account changes in the database ecosystem might be a better use of people's time.
Having said that, I don't have any specific proposal at this time - just pointing out that perhaps we don't want to keep investing in something which is showing its age a little.