The latest version of the .NET & J2EE Petstore is now available from The Middleware Company.  You can discuss on the ServerSide.  I won't give a long rant here, other then to say that TMC, by now, have probably the best industry knowledge of tuning J2EE applications.  There test matrix is huge, incorporating OS, app server, database, JVM version, JDBC driver and this doesn't even include what technology the app was developed using EJB, servlets, etc.  Really interesting read....