Query performance issue

Hello all,
I have a query which takes about 20 minutes to execute and retrieves
2000-odd records. The explain for the query is pasted here
http://explain.depesz.com/s/52f
The same query, with similar data structures/indexes and data comes back
in 50 seconds in Oracle. We just ported the product to PostgreSQL and are
testing it. Any input on what to look for?

Possible relevant parameters are
shared_buffers = 4GB
temp_buffers = 8MB
work_mem = 96MB
maintenance_work_mem = 1GB
effective_cache_size = 8GB
default_statistics_target = 50

It is a machine with 16 GB RAM.
Regards,
Jayadevan

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