It works on Windows! Opens sketch files, provides CSS and YAML as well as most basic Sketch functionality. Portable version available. FREE
A bit laggy and keyboard shortcuts are not all the same. It's still in beta though. This will only get better.
This is still in the early stages but I like what I see so far! As a product manager constantly working with designers, I can now open design files on PC for quick screen views, exports, etc. If that's your primary need this will be perfect!! If you are looking for a full featured Sketch replacement, it's not there quite yet.