I've been using Sketch for the last few weeks at work for a project I'm on. It's unreal.
I noticed the other day that they also allow you to create designs using iOS and Material Design UI assets, which literally blew my mind!
I would definitely use it in the future to quickly mockup my designs, get pixel dimensions etc once done then build them in WF. I think Sketch is easier than WF for really quickly getting designs onto a page (I sometimes find WF a bit trickier to go straight into, I have to mock it up first in InDesign!) but then for sure where WF is the bomb is adding interactions/animations and moving content.
P.S I think I heard from someone that Semplice are working closely with Sketch to let people build Sketch designs in Semplice more easily... That may be a rumour though!
Have you personally taken anything from Sketch into a web/app build? Would be keen to hear how it goes if you have/do in the future!