We were all left wondering when the Google wouldn't commit to a firm date for the Lollipop rollout, but now the OTAs appear to be happening. Sprint has posted update notes for the Nexus 5 OTA, which lists today as the big day. This should apply to all Nexus 5s, not just those on Sprint.
The update will have build number LRX21O, which dates to about October 21st, indicating no major changes have been made in the last week or two.
Sprint Says The Nexus 5 Lollipop OTA (LRX21O) Is Rolling Out Today was written by the awesome team at Android Police.