I have been playing around with the 2.5 beta and discovered an issue.
With the taskbar positioned at the left, It seems only left aligned start button works.
Also, I hid the start button on the primary display, and then unhid it. The start button did not reappear on the taskbar, however, if you click where it is supposed to be it opens the start menu. Restarting explorer did not help. Once any app is opened, then the start button appears, and then after all apps are closed, it disappears again.
This is a really cool addition to Start11v2.
pelaird
EDIT: Upon restarting the computer, the taskbar (on the left) did not populate the System Tray, and open apps do not show in the taskbar.