JBOSS versus Websphere etc

From my testing and reading on the Internet it would seem that JBoss is a very capable application server.

My question is two-fold.

What are people’s experiences with JBoss in a high volume production environment?

How does JBoss stack up to other application servers?

My thinking leans toward using JBoss in production with a service contract to Redhat (seems like the more affordable way to go compared to Websphere). My organization uses Websphere at the moment and from what I heard from some of my colleagues is that it is rather expensive and locks one into the IBM world.