I think automations in Ardour are cool, you can automatize pretty much everything, but there are a few things you cannot (or maybe I haven't found a way, so tell me!).
1. Send automation: it would be cool to be able to automatize the volume of a send
2. Mute automation: of course you could use a volume automation as well, but in this way you would be able to control the volume independently from when you want or don't want that track to play. Starting from that, there is a number of boolean value automations you could add, such as plugin activation, send mute, etc.