Here's a tip - I do a lot of development on other
J2EE platforms, noteably IBM WebSphere. The problem I run into constantly is the size of the server, how long it takes to restart, and having enough memory to run a development environment AND the J2EE server.
Tomcat solves all that for me. I develop under Tomcat and then port to WebSphere in the last week of the project. Wonderful!