• I often get a “shadow” mouse where I can see the Windows cursor and the Ubuntu cursor at the same time. This would make it difficult for me to know what I was clicking on.
• I usually have my Ubuntu VM at fullscreen on one monitor and Windows running in the other. In order to release the mouse from the VM I would have to hit Ctrl+Alt, which makes it tough to use the VM and Windows side-by-side. Also hitting Ctrl+Alt would exit the VM from fullscreen mode.
• The cursor would often flash in a seizure inducing way.

All of these issues can be easily fixed by installing the vmmouse driver. Which can be done with the following command:

sudo apt-get install xserver-xorg-input-vmmouse

After it is installed you can reboot or simply restart gdm with:

sudo /etc/init.d/gdm restart

You can now run the VM in fullscreen and seamlessly move the mouse in and out of the VM without having to press ctrl+alt all the time. It also fixes the other issues mentioned above.