Check these articles, I think the new features are really interesting:
Part 1-SQL and PL/SQL Features
http://www.oracle.com/technology/pub/articles/10gdba/nanda_10gr2dba_part1.html
Part 2-Manageability Features
http://www.oracle.com/technology/pub/articles/10gdba/nanda_10gr2dba_part2.html
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