A lot of considerations for VR design come down to mitigating motion sickness. Typography, audio, object movement- almost anything can contribute to motion sickness if done poorly. So while immersion, aesthetics, and user enjoyment are important aspects to consider in a VR experience, motion sickness should always be the primary consideration.
This document contains categories of VR design, with each category including tips and examples of good and bad design.
Check the bottom of this page for a link to all the references for this document!