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I am using Hexchat version 2.9.4 provided from the Fedora repository and I notice a small but noticeable delay when switching between tabs in the channel switcher, either by keyboard or mouse.
In case it matters, my switcher type is set to "Tree" and its location is bottom right. Everything also uses the Input Box style.
System architecture is AMD64.
EDIT: Come to think of it, I don't see the delay anymore, after a few hours the program is open. I wonder if it had to do with memory caching.
You can also try fiddling with toggling XShm during configure. Disabling it has helped eliminate the lag for some people.