I love Affinity Designer's speed for working with complex vectors. It's where I design my icons, then switch to Sketch for interface design work. Today I got an email that they updated the tool with UI tools, basically to directly compete with Sketch. I've used it all day and gotta say, it's faster than Sketch, and the responsive layout tools are pretty awesome. Not sure if it can replace my Sketch just yet thought (plugins and Sketch mirror), but it's getting close!