I love the new Sketch features and in fact they have been helping my current workflow a lot. I am in a project with a ton of complex forms. My symbols look a bit like this depicting every state of the form:

This is just 1 small part of the UI.

Lack of in context editing is the #1 lacking part to the implementation now. I often have to measure how many pixels I have to move something to make it "correct" and then apply it within the symbol.

I would love some way to have 2 panes open: 1 with your symbols and 1 with your designs. In fact I think I saw a screenshot with just that in an old thread about Sketch 3.6 but maybe I was dreaming.

The styles syncing is debatable, I don't think it's in the way of experimentation and direct manipulation. For me the situation that you are looking at elements on multiple artboards at a time occurs way less than the situation where an inadvertent change triggers a global styling change. For example if you have 1000 layers that use the "standard text" style, and you change it without remembering to make a new style or set the text to "no layer style" you effectively get into a massive beachball situation where Sketch is trying to apply your styles to many layers at once.

I also have some minor quips about not being able to detach a symbol until it's "focussed" (you have to left click first and make sure it's the selected artboard). I think that's just a bug.

By the way, did you know you can turn an entire artboard into a symbol? So you can prepare your states separately on small artboards and then match them together using instances. This might not mesh with some people's workflow but I love it.

Currently to migitate the in-context editing issue you can try the following: if you position your symbols close to the designs you are working on you can kind of do in-context editing if you have a large enough screen. But it involves a lot of direct manipulation to position the artboards correctly.

I also have to do a lot of "symbol hunting" now where I have to go and look where Sketch positioned the new symbol. I think it's placed right of the rightmost artboard but it can be pretty far. A trick to get to a symbol fast is to use Command + 2 to zoom in to a selected symbol in the layers list.