On every RT/8 device (including a few Surfaces) I updated (for friends and family), I made sure it had the current updates, including firmware, installed before installing 8.1. Zero issues. If you install a firmware update but don't reboot and finish the install, you're begging for trouble.
agree with JD88. As long as Microsoft doesn't have a Metro version of Office, the Desktop is a great plus compared to Apple tablets. I personally connect my Yoga 11 (RT 8.1) to an external display to do my Office work and it's great. That's the point of a Windows tablet: tablet + windows!