I think finer grained consistency models (as well as some other options) would be a step forward for RDBMS systems. However, that doesn't get over the fact that the relational model is not always the best fit for your data. This is especially true if your data is semi-structured. I work with the MongoDB/10gen team and we have a lot of users who enjoy working with the document model, and have seen drastic reductions in both amount of code and time-to-production from it.
Just a vocabulary/definitions nit: Data modelling (relational, document, data-structure, whatever) is an independent concern from consistency.
I may want ACID properties but over a document-structured store, for example, and there's nothing contradictory in such a desire...
In fact, as a continuation of my "mix and match" consistency pipe dream; I'd like to mix-and-match data models within the same system, too! Strongly typed w/ integrity constraints; bag-o-data; etc...
