Due to fixes and refinements, you'll want to upgrade if you're using any previous release. Or, if you're using Cobra from a Subversion workspace, you can just update at any time and run install-from-workspace in the Source\ directory.
Discussion thread / Announcement
See the ReadMe.text file after unzipping.
Btw if you're using Novell Mono, do not use version 2.2. It has one or more bugs which make it unusable with Cobra. Use 2.4+ or an earlier version such as 2.0.