Just got around to playing with virtualbox. A quick note on installing 1.5, you HAVE to emerge it from terminal. It asks you questions during the install that I didnt even know were there when I tried via package manager. It just failed over and over again trying it with a package manager. Went to console and emerged it, wham just fine after answering the now visible questions.
BTW if you play with virtualization at all, this is a must, if for no other reason than trying out seamless integration of guest on host. This coming from a guy who until last night believed that QEMU with KQemu/KVM was the only way that would ever make me happy.