Which LMS do you use and why?

We use Moodle 1.9x and have it working just the way we want after a lot of hard work.  We are holding off about another year or so before upgrading to Moodle 2 just because I don't have time to deal with the upgrade right now.  Moodle is great but not turn-key in most situations so unless you know the in's and out's of Moodle you'll definitely want to get help from a Moodle partner or independent consultant to get over the hurdles.  My biggest criticism is reporting like others have mentioned so we have had to develop our own custom reports.  That being said, what I like most about Moodle is that everything is customizable.  I'm no PHP developer but found most of the "Hacks" I needed in the Moodle forums.  Much like the Articulate community there are a lot of great moodlers in the forums at moodle.org ready to help.