1. Do you mean Hibernate compared to others?
Build on top of *real* needs,
We consider Hibernate to be a commercial equivalent (like Toplink).
http://www.hibernate.org/4.html
2. It is stable (my favorite answer), JBoss Inc has a professional support for Hibernate
http://www.hibernate.org/148.html
http://blog.hibernate.org/cgi-bin/blosxom.cgi/2004/04/02/
3. Most people using it cannot talk about that since it's in corp usage.
http://www.hibernate.org/113.html
[url]forum.hibernate.org[/url] is high traffic
JBoss is reimplementing it's CMP engine on top of Hibernate