TouchWiz is nice this year. Like a major upgrade. Just don't kid yourselves into thinking it's as good as stock. It's still jarring coming from such a simple elegant experience (stock).
While stock is elegant, especially now that we have lollipop, it wasn't in the Kit kat era: it was 'simple', but not elegant. Stock android is also lacking in features and is far from ideal. For example why can't i have a ,as my main screen a page without widgets or shortcuts and anothe one on the right wit the calendar? Stock android doesn't allow blank screens. Most launchers allow this, but google launcher doesn't.
TW needs optimization, but that's it, it is not better or worse than other launchers/UIs, it is just different.