  The Southern part of the Pierre Auger Observatory is nearing completion, and
has been in stable operation since January 2004 while it has grown in size. The
large sample of data collected so far has led to a significant improvement in
the measurement of the energy spectrum of UHE cosmic rays over that previously
reported by the Pierre Auger Observatory, both in statistics and in systematic
uncertainties. We summarize two measurements of the energy spectrum, one based
on the high-statistics surface detector data, and the other of the hybrid data,
where the precision of the fluorescence measurements is enhanced by additional
information from the surface array. The complementarity of the two approaches
is emphasized and results are compared. Possible astrophysical implications of
our measurements, and in particular the presence of spectral features, are
discussed.
