To followup to my own post, Oracle has a new whitepaper describing the differences between the 4 (!) editions of the 10g database product:
http://otn.oracle.com/products/database/oracle10g/pdf/twp_general_10gdb_product_family_0104.pdf
The two most exciting things about this to me are (1) RAC is now part of Standard Edition, and (2) Standard Edition now supports functional indexes. I haven't dug into the technical details of that yet, but there is the potential for some huge performance increases there, especially creating indexes on things like 'lower(first_names)', 'lower(last_name)', and 'lower(email)'...
