I would find this useful too, especially on laptops where you switch between Wi-Fi and Ethernet. Having the current connection speed visible in Firefox would make it much easier to spot when the network has suddenly dropped to a slower link. It would be even better if it showed the connection type and negotiated speed separately, since that’s different from the actual internet speed. For example, seeing that Wi-Fi is connected at 866 Mbps while an internet speed test is much lower would make troubleshooting a lot easier. For anyone checking their router or network settings, knowing the local router address can also be useful.