VirtualBox marches on with the new version 3.0.6 maintenance release focused on performance and stability. If you use AMD, then this is Christmas morning And a few Snow Leopard wrinkles were ironed out too.
When I create new Virtual Machines, or guests, in VirtualBox I tend to skimp a little on the size of the virtual hard disk I create because I'm trying to save on host disk space. And this tends to come back and bite me when the guest quickly fills the disk and I run out of disk space in the guest. So you think, "wait a minute, this hard disk is just a file, so why can't I make the file bigger?".