Which LMS do you use and why?

My company has gone with ShareKnowledge, from Competentum.  A company that made Kisperski software.  We went with it because it "bolts" onto Sharepoint.  It is not a cloud service based LMS, but has a good interface, and uses all of the old and newest SCORM formats.  Enrollment rules make it easy to pinpoint a title or person or department for training, and security features through sharepoint allow for shared AD databases.  It will integrate with AD or manually uploaded CSV files for employees if you choose to go that route, or you can upload the personnel manually if you don't have a bunch to input.