I like that it has many options for managing certificates, including self-signed ones! It's also very easy to use (and free!).
Sometimes there is an issue with cert renewal but this isn't always as bad of experience when compared against other certificate management software/services out in market right now such as Symantec or GoDaddy certs etc.). The interface can sometimes be confusing if you're not familiar which makes using CertMgr more difficult than necessary at times - however getting used takes less time then expected once they are explained well enough by their support team :) We have been able solve our problems related security quite easily since we started working together via email & phone calls so far everything seems pretty smooth going forward too us!!