Ben,

I've been working on the Rlabkey package for the past couple months and have fixed many bugs related to null handling and also the extra link info that comes from the server on a lookup field. We haven't released this new version to CRAN yet (we are waiting on a change to rjson that will give us a bid speed boost) but I have attached the current package for you to install as a zip file into R.

There are also a set of new apis that make it easier for a R user to work with the data in labkey; see getSession and related apis.