Hi Stephan,
I'm not sure what your problem looks like: I can do the following without any problems:

>>> import pygiftiio
>>> image = pygiftiio.gifti_read_image('test.gii', 1)
>>> darray = image.darray.contents.contents
>>> print darray.nvals
466941

Keep in mind that I am trying to leave that majority of the bindings as close as is possible to the C library so that developers can write their own wrappings for things. The GiftiImage class contains a POINTER(POINTER(GiftiDataArray)) as dictated by the underlying C-struct. This requires 2 levels of redirection to get at the GiftiDataArray class on the Python side.

Hopefully this will help!
Thanks,
Erik