The things I find super-handy are;
Being able to define 'Environments' with multiple variables; enabling me to switch sending requests between Dev, Staging, Production etc.
Able to share a 'Collection' with my team via a link.. If I make changes, I can hit update, and everyone can download my changes without any hassle (or re-keying them)
It'd be great if Jive maintained a shared Collection with a bunch of sample calls that are validated as 100% working.. then it'd be a good starting point for anyone to jump in and adapt the REST call to their environment & needs. I've started my own version of this which contains some things that are specific to our environment, but this is the idea;
Even if this isn't practical for Jive to do this & keep it up-to-date, any developer working with the REST API should look into this tool.. it rocks