I have listed my comments below. I just want to make a few points. They don't necessarily all flow together.
1) The concept of heirarchical data objects as opposed to object mapping makes more sense when you have a relational datasource to begin with.
2) Your implementation and explanation is very short, sweet, and clean.
3) I would be careful to compare what you currently have with .NET's dataset because you are missing quite a bit that they are offering ( sql query'ing, relationships, and a mountain around it just as databinding). This is not to say that aspire couldn't be expanding to incorporate these.
4) I think you shouldn't be giving this away for free. Firstly, people won't take you seriousely if you give it away. Secondly, it is worth far more than nothing.