I solved one of those mysterious slowdowns that afflict some owners. I have a fairly small network, not many apps or rules. Mostly motion sensors and light switches. A couple of days ago it got slow - 2 or 3 seconds from motion to lighting. And over that next few days it stretched to 5 or even 8 seconds. Web page access was slow. The delays were visible in the log. But no errors or obviously misbehaving device or app. On a hunch I reboot my mac mini - not the hub. Things cleared up quickly and its back to sub-second response.
I have a Mac Mini with Firefox and 3 or 4 tabs open to HE. 24x7. I also have an Ubuntu box, also Firefox with 4 HE tabs open, 24x7. Like the title says, It's just one data point but it might help the search for resource constraints.