I'm not having "not responding" and "unknown error" message so often; they happen, but less. And for me, edition has become a faster process since 4.3 that happen to be less stable than 4.2 and 4.1 versions.
Slider performance in Develop is certainly snappier. But that's probably because of pixel-doubling that is used since 4.3 (but had a bug in that version). I, personally, am happy to trade some pixel-doubled sharpness for performance while dragging the sliders.