I'm currently using Cosmic JS for a personal project, and so far I've been really impressed -- I was able to launch my site in under an hour, and that was starting completely from scratch with no prior knowledge of Cosmic and having never used a headless CMS before.
One thing that helped a ton was the availability of pre-built templates; there happened to be a node app template that fit my frontend use case perfectly, so I was able make the tweaks I wanted and launch.
One thing that helped a ton was the availability of pre-built templates; there happened to be a node app template that fit my frontend use case perfectly, so I was able make the tweaks I wanted and launch.