I'm pretty sure I have mentioned it in one of the VirtualBox announcement posts: if you have an existing VMware VM disk image with your OS installed in it, you don't even have to convert it when you switch to Sun xVM VirtualBox. Booting VMware VMs with Windows hangs in VirtualBox VirtualBox natively supports VMware [...]

Sun Microsystems has just released the maintenance update to VirtualBox product, so xVM VirtualBox 1.6.2 is available for download. Looks like version 1.6.2 is well worth the upgrade, at least for 64-bit PCs. I'm also happy to see many of Linux and Solaris host-related fixes, the stability of VirtualBox has really improved since version 1.5.