I usually have one long-lived instance of an editor for the project/thing I'm focusing on, but I also frequently fire up "temporary" instances for one-off editing jobs, from the terminal.
The difference between, let's say, "subl ." (launch Sublime Text in the current directory) and "atom ." is staggering: Sublime Text starts instantly with a boatload of plugins; Atom starts nearly instantaneously but then takes around 5 seconds to become usable, without plugins, after repeated runs.
(Speaking of specs, I'm on a late 2013 Retina MacBook Pro, 16 GB of RAM)
I will switch when Atom gets more stable (I still encounter bugs everywhere), and more performant.
I have already developed a plugin for Atom, I hate the living shit out of Coffeescript, but I like Atom's API. It's a shame that the spacepen API was built in such a way that it's unbearable to write plugins with it in pure js.
In relation to your side note, perhaps a site like http://html5up.net/ might be of use. I'd be interested if others have other similar resources they use.