I will be migrating a websphere application to tomcat. I've read these online docs - http://blogs.mulesoft.org/how-to-migrate-your-weblogic-or-websphere-app-to-tomcat/ & http://www.mulesoft.com/downloads/Migrating-from-Websphere-to-Tomcat-Mulesoft.pdf
I also found this helpful - What are the differences when deploying on Tomcat vs. Websphere?
From reading these docs it seems like it's a not too difficult task, at least on the face of it. So any J2ee/EE functionality that the app is using which tomcat does not implement needs to be added manually, this may include changes to the code base to support the tomcat server.
Are there any technical details/pitfalls I should watch out for during migration?
How can I effectively estimate the amount of time this migration should take ?