Let's for the minute set aside the problem of how slow it often is to download the plugin list.
And how slow it often is to download a plugin.
But IntelliJ is still the best IDE by miles.
Setting aside all that.
Say it's slow to download a plugin - could be our network that's using carrier pigeons to transfer the bytes.
If I click Cancel (decided I don't really need a pacman plugin), the dialog box does not cancel immediately.
It sits there for ages waiting for some network timeout or something - we're talking a minute or so. And in the meantime IntelliJ is frozen - my fellow developers often just kill the process.
It'd be fantastic if the Cancel would work instantly.
I've also noticed this behaviour in other areas of IntelliJ but can't recall the instances. I know it's a pain to write the extra threading code but it is so worth it.