1. Support for inheritance in code-behind files, so we don't have to (a) create a project and build an assembly for the base class, or (b) use KellyCoinGuy's hack and throw base classes in the same file with descendant classes.
Example:
public class MyCodeTemplate : MyCodeTemplateBase
Have it look for MyCodeTemplateBase.cs in the current directory (or possibly a SearchPath attribute).
2. Better support for views. TabularObjectBase and DataObjectBase don't provide enough functionality. For example, there's no TabularObject property on DataObjectBase, and no DataObject[] property on TabularObjectBase. Our company uses views and tables almost interchangeably.
3. Improved documentation. The API reference is incomplete, code behind is not explained well, the tutorials do not cover many of the features, etc. You've got a great product. Hire a great technical writer to show it off.