1) I had built a system around svn to automatically build and deploy a webapp, the deployment was made via the Tomcat ant tasks, and with antiJARLocking and/or antiResourceLocking to false the application was not undeployed properly, because tomcat could not delete some jars and the log4j.properties config file, thus the deploy failed. So I had to set these properties to true, and tomcat did a copy of the webapp in the temp dir. This makes the deployment slower and with nearly each redeploy the temp dir grew in size, so I had to make a procedure to delete older deployments of my app from the temp dir. It is safe to delete deployments from the temp dir at any time, because tomcat will redeploy the app to the temp dir.
2) From the tomcat docs I understood that the problems with jar locking or resource locking occur only on Windows. I wouldn't set these properties to true in a production environment, because there's no need to redeploy so often, and with java it's always a good idea to do a server restart after redeploy in production (an OutOfMemoryError is always lurking in the dark, even if your own code doesn't leak). Another minor issue is that the app being deployed to the temp dir, if you modify a jsp or another file in the webapps dir, it won't be redeployed unless you copy the changes to the temp dir also.