I've been happily using sway everywhere I've found it to be stable. At the moment that's every machine I have access to that has intel or AMD graphics. I think my one system with nouveau graphics may be ready to convert from i3 also, since I've been trying it periodically and it seems to be OK. The one machine I'm still scared to touch has to use nvidia because it flat-out refuses to work with nouveau. At any rate, I'm quite pleased with sway. It's compatible with i3 to the point that I often forget which one I'm using.