Have you used the OpenAccess ORM from Telerik? How does it compare to NHibernate? When should I consider using it over NHibernate?
I've not used it but one benefit obvious to me, is OpenAccess is supported by Telerik, where as nHibernate is supported by the community. Depending on your company this can be a deciding factor if your ready to embrace open source solutions with no guarentee of support.
For the record I am a big supporter of nHibernate, and open source in general. I have been using nHibernate for the last six months, using it for all new work in our web application. For my current company it is a good fit (Startups love free).
However, my previous employeer, would have had a very difficult time accepting a community supported component as a core piece of their infrastructure. This is perfectly reasonable as these companies' web sites are their sole source of revenue. Would you want to stake your entire business on software that has no accountability associated with it? Some people wouldn't want to take that risk on.
Personally I have found the support for nHibernate to be on par and even better with some commercial vendors.
My point is not to bash OSS, but to highlight one benefit of using software that has a coporate backing, with a fully staffed and dedicated support channel.