How long does it take for a message published on a PubNub channel to be received by the subscribed clients?

PubNub's goal is to deliver messages, end-to-end, within 1/10th of a second (100ms). The vast majority of delivery time is spent within the connections between the publisher app and the subscriber client. Therefore, PubNub keeps adding data centers globally in order to enable apps and clients to connect to the nearest PubNub servers to achieve optimal performance. You can see for yourself PubNub's recent and historical performance stats as reported by Pingdom, including uptime and latency.