The number of bug reports about S11 is very low but with millions of different configurations and the way people use products things can quite possibly have been missed.
Sorry I did not see your original post and the bugs don't seem to have been created in the bug tracker. Apologies for this.
Having located your original post I can give you some answers:
1) With your mouse issue on all apps I notice you say scroll button on your mouse, not scroll wheel? What type of mouse is this as the list supports touch pad scrolling, wheel mouse scrolling and touch screen scrolling as well as arrows on the keyboard. But if you have a button on your mouse perhaps for up and down that would potentially point towards a very unique implementation of scrolling perhaps by sending page up/down? So far we have no other reports of this so I will await your response on mouse type so see if we can track down the root cause further.
2) The highlighting thing sounds like it is a colour scheme issue. So the active mouseover colour is basically the same as the colour of the background of the menu. Have you set a custom colour for Start11?
3) We are aware there is a potentially 1 pixel gap under the Win7/Modern menus when set to not be offset from the taskbar. This is being addressed. If the gap is larger than this then it will be the option in Start11 to offset the menu from the taskbar being turned on under Visual Effects.
4) Animations should be just fine as of the 1.01 update. 1.0 had a problem on some computers where the timers were not running smoothly and causing frame drops, but this was resolved in 1.01. I am pleased to say the feedback on this from those who reported the issue has been positive and the problem appears resolved. It wasn't a problem on all computers.
Jafo : Start11 is intended to replace Start10 on Windows 10 too. It offers a great deal of new functionality to those on Windows 10. That said I agree if you hit an issue with S11 then rolling back to S10 if you already owned it makes sense.