I started backporting proj 4.6.1 to bpo - which fixes the datum shifts issue for lenny.
My own idea is minimally backporting also gdal 1.5.4 and grass 6.4 with the grass plugin.
After that I would move in sid currently experimental packages (mainly gdal 1.6 series).
In the meantime I would also prepare the final version of the HDF5 library.
It would be nice if people would note here if they are interested in backporting
other relevant packages (maybe mapserver or postgis?)
Francesco P. Lovergine