In Safari I always have ClickToPlugin enabled, and only load Flash when I really have to. However, some of my newsfeeds put Flash embeds in their content, and since I browse in Unified layout, Vienna ends up loading all of them. This ended up pegging one of my cores at 100% today. I would love it if Vienna had an option to disable plugins, or make them load-on-demand like ClickToPlugin does.
ClickToPlugin is a Safari extension, and Vienna does not handle them.
But Vienna handles traditional Webkit extensions. I personally use ClickToFlash 1.6b20-ssp, that you can get at Earthlingsoft. It works correctly on Mountain Lion, alongside with ClickToPlugin.
The only problem I have with it is with BBC's website. You get a message "Cannot play media. You do not have the correct version of the flash player. Download the correct version", even if you disable Flash blocking.
@ssp 's source code is available here, so, if someone is interested and has time to investigate, I would be very happy !
I'd still like to request this feature extension-less; that would be more useful and less brittle.
It would be nice if there was an option in the preferences to disable the whole plugin architecture like it is possible in Safari (just a simple single toggle is enough, I don't feel the need of granular options Safari 7 has)