Apache Hadoop 2.0.4-alpha is now available.
This is a bug-fix release which fixed a number of integration issues that were uncovered with hadoop-2.0.3-alpha.
Please see release notes for details.
Also, this is most likely the last of the hadoop-2.x alpha releases. The Hadoop community is gearing up for a final stabilization push of hadoop-2.x and should release a final hadoop-2.0.5-beta in the next month or so. After a short period of further testing hence, that beta should be the precursor for a stable hadoop-2.1 release this summer.
Arun C. Murthy