It should work, I upgraded and have no problem.
You should double check if you have privilege to use port 80. In windows, you need "Administrator" to use port 80. In Unix, you need "root" to user port 80.
It works now.
Except modify the jboss-service.xml under the jbossweb.sar.
I also modified the jboss-service.xml under http-invoker.sar and under the jmx-console.sar.
I found that they hard-code the http://localhost:8080/....
I just changed the port from 8080 to 80 in $JBOSS_HOME\server\default\deploy\tomcat41-service.xml. Seems to work fine.
(I use jboss-3.0.4_tomcat-4.1.12.)