Our experience with Enterprise LMS such as Saba (past) and Plateu (current) hasn't been great. Since I am involved in Application support, my group has been through many painstaking & frustrating hours of discussions with Platue support for getting desired technical support. That lead me to analyze the Open source trends around Learning Management systems.
The Open source LMS platforms are quickly maturing. Leading the pack is Moodle (www.moodle.org). It's modular in design and allows new modules/ plugins to be incorporated with core modules. Moodle has developed a significant user base among SMEs and educational institutes. It has currently around 36000 registered sites with 1.4 million courses. Available under GNU GPL and is OSI certified.
Other worthy competitors are
Checkout the eLearning Guild Press Release for market leaders in LMS platforms.