This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
There is no harm in the you choose to do the mapping. Similar behavior can be achieved by setting welcome file as well. When you configure more servlets they won't impact the existing ones as every servlet is required to have a unique URL pattern. Two servlets can not have same URL pattern though one servlet can serve many URL patterns.