Atul,
> 2) Do I need to upgrade JDBC driver when I upgrade to postgres9.0.
Yes, at least if you use BLOB types. The 9.0 server sends them in a
format former JDBC drivers cannot understand:
http://www.postgresql.org/docs/9.0/static/runtime-config-client.html#GUC-BYTEA-OUTPUT
Other than that I did not experience issues, but the application I
support was upgraded from only 8.3 to 9.0 (and is running now on 9.0 for
many months flawlessly).
Best regards,
-hannes