First of all, JRebel is amazing. In an effort to reduce development time, I ran across JRebel (thanks Christian), a tool that allows you to reload a webapp (jsps, classes, jars) without the need to redeploy the entire application.
So far, I've been able to configure Eclipse/Tomcat to hotswap classes from OpenMRS core and modules without the need for redeploying the entire webapp. I'm currently working on getting the JSPs to be reloaded on save from within Eclipse, rather than requiring us to run deploy-web.
Download JRebel from the ZeroTurnaround site
Very exciting. More details about how to configure JRebel coming soon ...