J2EE Developer Migrating to SAP/Netweaver

I am an experienced J2EE developer with over 3 years experience in writing JSPs, servlets, custom tag libraries, etc. I have written web applications that utilize SQL Server, MySQL & HSQLDB. In addition to the programming aspect I am also a pretty well rounded DBA with a healthy SQL background.

I tend to work strictly within the J2EE framework and <b>don't</b> use OR tools like Hibernate or Spring, <b>nor</b> other application frameworks like Struts, Tapestry or JSF. I have multiple custom tag libraries that I've written over the years that I use to speed up application development.

My typical development environment includes using Eclipse with the MyEclipse J2EE plug-in, using Tomcat (for web applications) or JBoss (for Enterprise applications) as the application servers.

I have been asked to join a firm writing J2EE applications (I assume including Portals with iView) but I have not experience with SAP. How steep do you believe would the learning curve be before being a productive developer in this area? What are the biggest differences between developing in a complete J2EE environment vs. developing within the SAP Netweaver environment?

Thanks for your assistance.