Just installed version 345 and everything is back as it was.
The mouse is very sensitive again, I only have to turn it very slowly to change to a new page.
What can it be that changes my mouse sensitivity between the old and new version ?
Yes there are still some subtle difference. Most noticeably Build 346 differentiate page-turn-mouse-wheel from regular page-scroll-mouse-wheel. eg, when scroll to the bottom, you need to "release" the wheel and scroll again to turn page. That's the "lag" you noticed, but it's harder to turn page by accident this way.