ODBMS trade-offs
Younger technology; standards have developed and continue to emerge
Efficient for deep hierarchies, complex relationships, and referential integrity
Efficient for object-navigation queries
Performance of value-based queries depends on specialized techniques
Notes:
The greatest disadvantages commercially for new OO GIS systems is nothing to do with the OODB/RDB trade-offs, but entirely to do with the maturity of the RDBMS products in terms of hardware-specific optimizations, back-up and recovery infrastructures, the availability of SQL programmers, and especially the non-technical benefits of well-known brand names and established, profitable companies.
The Universal Server OO/RDBMSs, coming as they do from established RDBMS companies, and using their existing backup and recovery mechanisms, avoid these difficulties. However, the new pure OODBMS 'Jasmine' from Computer Associates is worth watching.
The OO, ODBMS and GIS communities are actively working on standards at many levels (to be discussed shortly).