I really dislike how fonts render in Sketch. There used to be a option to sub-pixel anti-alias fonts but they removed it for "performance reasons, and improved consistency with mobile platforms".
I understand not everyone wants it but that was the beauty of having it as an option. Now it's just gone and those of us who do want it can't use it. Personally I never had a performance problem with it (plus it was off by default) so I was (and still am) very annoyed at it being removed.