A 10-15% speed bump in CPU performance is certainly nice but in most cases it's not going to be something that users are consciously aware of. Web page performance varies a lot due to network performance, new versions of websites being deployed, different ads being served, and so on. This noise obscures things enough that it probably won't be easy to attribute a change in performance to the browser if you're not looking for it.

But even if the users aren't aware of what changed, it will likely affect user behavior.

For the better? Hard to say. Websites that load a little faster are a little more addictive.