There are a couple of things I think could be improved in the GUI for showing the content of a datastore: currently all corpora and documents are shown in a tree-like display, but that can cost a lot of performance if there are really a large number of documents in the corpus.
So it would be better if the list of documents would only be shown on demand, so opening a corpus from the datastore would not necessarily cost the overhead of showing all the documents too.
Also, it is practically impossible to locate a specific document in the document list: the sorting order seems to be totally random and cannot be changed and there is no way to find and mark a specific document in the list in order to delete it or load it (in my case I had to find it because GATE hung and killing it caused the serialized version of a document to become destroyed and unusable)
First part of this has been fixed by checkin of revision 15671 see http://gate.svn.sourceforge.net/viewvc/gate?view=revision&revision=15671