My question really was ambiguous and more to do with subtle frustration with limitations of the current DF library and the dependence of various nice statistical features in GLM, or plotting in Gadfly, that rely on DataFrames. It's not just nullable types (and also I believe the Nullable arrays in DF are tuned for performance with linear algebra operations, which may not be true for general Nullable arrays). You can get to the features in other ways, but it's easiest to use DataFrames and the documentation is written for DF's. However I think the documentation, scope of functionality for DataFrames, etc is not complete enough for me to quickly use it day-to-day. So I basically just put everything back into arrays and do a couple of custom functions to get my work done. Julia makes this great, but it'd be better to not need to and MATLAB still has many more "easy" functions along these lines.