I'm not sure I qualify as a "heavy user" but I can say that with Vue 5 infinite I had to divide my current scene (part of a big project) into 3 parts to avoid "issues". With Vue 6 infinite I have not ran into this kind of problem and am assembling the whole thing in one scene.
Over all the Vue6 seem more stable, more alert and renders faster. But considering the improvements in Vue6 the "wants and musts" have become greater which at the end gives longer render times.
I liked Vue 5 a lot but I really love Vue 6i!