The ease at which I can purchase multiple certificates for different domains/subdomains or subfolders without having each one expire separately was very useful! We used it mostly as part of our PCI compliance process that required us purchasing several certs from Comodo, but we also use them internally when testing new features before going live so they were handy too!! Price - It's expensive compared against other providers (even if you buy more certifications).
Some people may find this offputting since their budget doesn't allow much spending money up front like most companies do nowadays; however, once your project gets under way then there are no issues because all future renewals come out automatically through auto renewal options provided by CertSimple themselves via email reminders etc., just make sure not forget these emails otherwise things could get messy later down the line.