We were doing a performance test of EF 5 and EF 6(alpha) against NHibernate.
Our test consisted of inserting records in one single table (without constraints, etc), running multiple threads. We found that EF 5 was of an order of magnitude slower than NHibernate and EF 6 was a bit faster but still about 3 times slower than NHibernate.
EF 6 was inserting approx 75K records in a minute and NHibernate managed about 250K/per minute. The entity in both the cases were POCO. We would like to know the reason for such a low throughput, since we are evaluating both ORMs for our new project and would prefer to go with EF since we are a MS shop.