Why choose our LMS/LRS when there are over 600 other systems available, especially when many of them are free? The answer depends on what you need.
Many systems are significantly more powerful than Comet. Blackboard, for example, allows for extensive communication (chat, mail, discussions...), content creation... but online criticism of it as slow and unreliable can often be traced to poor configuration by local system administrators. And Moodle includes capabilities that are impressive yet you can readily find people who claim that it is "hard to use".
The last time I helped install Moodle I remember spending the best part of a week getting the basic functionality working the way the client wanted. While I can appreciate how a system that encompasses many, many features may be time consuming to configure I still like the simple things, simple.
With Comet, installation and configuration (not including the MS SQL Server database configuration) is basically copying the files to a web server, setting some folder permissions, and being able to write a connection string.
True, that one caveat is that if you upload a lesson (a SCORM compliant or Tin Can compliant course) and then you later replace the lesson with completely different content it could cause issues when a user tries to resume the lesson they had started but if you pay attention to what you're doing then there shouldn't be any problems.
So choose Comet if you prefer working with a system (doing your work) rather than on the system (trying to get the system to work).