Me and 5 of my friends who are also web/mobile designers moved to Sketch two years ago, during this two years I maybe had 2 or 3 crashes, and none of them affected my workflow because of the autosave feature of Sketch.
That said, most of these things can be worked around, and the benefits of Sketch are enough that a lot of designers can overlook them. Personally, though, I'm probably going to switch full-time to Affinity Designer once symbol support is released.
I actually own Designer (and Photo) but purchased Sketch to better integrate with some of our UX team workflows. Designer is stunning, rock solid, and I've never had a single crash or undo issue (or font rendering/scaling, or grouping, or or). Sadly no one I know uses it; it's all Sketch these days except for the Illustrator holdouts. I've asked a few of the prototyping tool folks like Framer to import the Designer file format like they do Sketch. I believe it's documented and would help encourage adoption...no news yet.