I have been chasing Virgin Mobile UK for a while now to find out when the official OS release would be, without success. Used DM today and found the upgrade ready and waiting.
Bundle 7.1.0.1149
v7.1.0.342, Platform 5.1.0.276
Have just upgraded via DM, not sure if it is available OTA.
No issues so far - will report back if I find any.
WiFi hotspot works. Battery life is much better, but I have also disabled compression in storage, so not sure which is causing better battery life (hopefully both).
Only problem I have had so far is App World is very laggy - not sure if this is directly linked to OS7.1 or not, but battery pull sorted this out, for the moment.