Hi
http://www.polepos.org/ has some open source benchmarking. I didn't find any "Hibernate" circuit, but the authors talk about Hibernate in the principal page (and not very good i must say...):
"The use of O-R mapping technology like Hibernate or JDO O-R mappers has a strong negative impact on performance. If you can't compensate by throwing hardware at your app, you may have to avoid O-R mappers, if performance is important to you. Protagonists of O-R mapping technology may tell you that caching will bring you back performance. Although this may be true, do not forget: Data that comes from a cache can always be stale in a multi-user application. If you want your data to be up-to-date, you have to reread from the database and an old cache that you can not use will even degrade performance."
I think this statement is very generic and coarse-grained, anyway...