Irritated by the small toolbox that pops up on the seamless mode?
some suggested adding a new toolbar so that it will be like double decker.some suggested removing it. http://superuser.com/questions/154182/remove-virtualboxs-lower-machine-configuration-bar-in-a-running-vm
I do not recommend it as it is sometimes handy.
So, my fixed-it solution for now would be to set the size so that it is just big enough to dwarf the irritating config bar.
Another solution is to hang the toolbar upside instead of keeping it down there on bottom.
Less annoyance is always good!