I am thinking about using NHibernate 1.2 but I am still at the research stage. Various online references have stated that to obtain additional performance benefits, mapped classes should declare virtual properties/ methods or support an interface.

Is this performance benefit another way of saying many applications should make use of lazy loading and lazy loading is dependant on the ability of NHibernate runtime to create proxies to mapped classes?

I am keeping my fingers cross that the full answer might be that proxied objects automatically implement a high performance is-dirty change tracking mechanism.