Ex Libris released V. 20.0 in Spring of 2009, in the Fall they released 20.1 and v20.2 came out in early August 2010. The SULs are currently on V.19.
The plan is to upgrade the operating system (RHEL5), the database software (Oracle 11.2) and the Library Management System (Aleph v. 20). We will be upgrading all instances within the same downtime window.
The Oracle upgrade from Version 10 to 11 is the biggest technical change and will take the most time, while other Aleph sites report that the Aleph upgrade to V. 20 is fairly smooth. There are a number of desirable enhancements.