Don’t forget multiple windows too 
What I find annoying is that you can’t have a project spanning windows. Say you
have some project specific settings that are used to mod the behaviour of some
plugins you have.
Say you have 3 monitors and say you drag out a tab from the project window into
a second window. Cool, it’s already been given the setting right, so all is
fine?
But what if you use some open in same folder quick panel command to open a few
more files in that second window? The project specific settings aren’t applied.
As well as multiple groups / windows the handling of clones seems less than
optimal.
Clones have implications for plugins. I’ve never really sat down before and
studied it, having only in the last few months started to use them extensively,
but I’ve been dimly aware of some quirks. For example I noticed that SublimeLint
(not SublimeLinter) will only work in ONE of the clones and sometimes not at
all.
Views have an id(), but also a buffer_id(), the latter is what’s shared between
clones. The add_regions regions and view.sel() selections are not share though
the view.settings() object is.
Settings being shared has interesting implications if used for tracking state on
your plugin (settings are easily referenceable out of the box via bindings and
not an uncommon way of tracking state)
I just looked then and found that event handlers DO seem to be fired for each
clone, but curiously the handlers are passed the same view multiple times? This
can be quite easily determined by comparing the id() of the view passed to the
EventListener and the window.active_view(). It’s not even always the
active_view() that gets passed to the EventListener method.
This could easily be the cause of havoc on stateful plugins I’ve been noticing.
I’m wondering if there’s any reasoning behind that or if it’s just a bug?
Perhaps it’s there to make the case of handling single views easier?
Like multiple selections, I’d guess a bit more attention needs to be paid when
developing for multiple views. IIRC The TextMate guy used to say multiple
selections were too complicated. I think everyone’s on the same page with seeing
that the additional complexity cost is worth it though.
Likewise, I’d say the same with clones. They are far too handy to have to choose
between them or other handy plugins that don’t operate with them.