I can confirm it: upgraded from 14.04 to 14.10 - no problem. Then 14.10 to 15.04 and reboot. Mouse pointer not visible. Reboot and moving the mouse while logging in - mouse pointer appeared and stayed.
I can confirm it: upgraded from 14.04 to 14.10 - no problem. Then 14.10 to 15.04 and reboot. Mouse pointer not visible. Reboot and moving the mouse while logging in - mouse pointer appeared and stayed.