My rings final arrived today. Sizing and quality were outstanding.
I am running the latest build of Windows 8.1. Nokia 930
I was able to load my contact card and it works great, touching other NFC devices handed off my full "Contact Card", so well done.
One thing I did notice that the defaults loaded on the ring took me off to the nfcring website and asked me to download the app. Problem is it sent me to the Google Play store rather than the Windows Marketplace. You may need to update your code on that page to test the browser that is making the request and send to the right store.
Other than that great experience.