From my personal experience Sketch is now in a state in which I consider it suited for production work: Sketch is helping me getting stuff done far more often than hindering me in my work. There are still bugs (and there always will be bugs, it's software after all), but they are no dealbreakers (for me). Sketch has reached a point where I'm satisfied with its overall quality.

Admittedly, sometimes I'm still reminded of the bad ol' days when it sometimes took me minutes after an update to find major reproduceable bugs: When 3.3 shipped and broke click-through measuring, an essential feature, that had worked for the last 2 and a half years I was once again asking myself if Bohemian Coding actually uses their software, how they cannot find something like that and how this can be shipped to customers. I still find it amusing, that it even was mentioned in that article detailing all 3.4's "new" features, when it was finally fixed in the last update.

In the end, however, I have to say that there is little software on the Mac I feel so strongly about as Sketch. When everything works (and nowadays this is 95% of my time) it is an absolute delight to use. I feel I'm quicker and more efficient than I was or ever could be with any of the competing offerings. I love the little touches, the clever ideas, the wide array of extensions and I hope that with the ever growing support (and hopefully, financial success) of Sketch they further improve the overall software quality and keep on adding features, that make my daily work easier.