So my experience with RNDR so far has not been very pleasant. Just wanna share my experience so someone else doesn't get burned. Two days ago i decided to render on RNDR cause i am on a tight schedule. The render finished pretty fast but i couldn't download my file. After contacting support, they concluded that the problem was the output file was too big and that was causing the error (I had a 32bit multilayer EXR).
They suggested that i disable multilayer and try again, and they would be willing to refund me for the scene. It was too late since i had already rendered the scene on my machine. So not only did i waste money, i wasted a whole workday, and i still didn't get a refund. So when you render on RNDR, try to keep your output files small i guess.