I use InDesign CS6 to create ePUBS. I find the conversion to be much improved over previous versions. My only gripe is that footnotes are automatically placed at the end of every chapter instead of at the end of an entire document.
Afterwards, I use a standard HTML editor (in my case, Espresso) to touch up the CSS. I've always found Sigil to be unstable and buggy, and am not particularly impressed by its features.