VirtualBox 2.0.0
The new release of VirtualBox includes the most lacking feature for me: 64-bit guest support. I'm considering what it would take to move back from my current KVM/QEMU/Qemulator setup. I'd have to convert my qcow2 images back to vdi which is not an appealing prospect. At one point I had heard that there was a consortium working to design a cross platform disk image format and I wonder what became of that. The only format supported across the board is VMDK but there are performance penalties for several virtualization solutions (QEMU/KVM/Xen) as well as compatibility issues. I'll probably stick with my current setup but I am interested in seeing what VirtualBox has to offer in this new release. Perhaps I will at least begin recommending it again as a desktop virtualization solution. The best information about VirtualBox 2.0.0 is available in its ChangeLog.
Actually...
It's actually quite trivial to move from one to another, assuming you have a DVD writer that is.
1. Boot in your VM from an imaging tool (Ghost first comes to mind).
2. Image the VM to DVD(s)
3. Boot your new Virtualbox VM with those DVDs.
4. Restore.
While that is a creative solution...
I think it would be easier and faster to simply convert the images, from Qcow2 to Raw, then from Raw to VDI. DVD read and write times would be longer than I would like to spend on the process. Plus I try to avoid paying for software like Ghost. Though I suppose one could use partimage instead.