I don't know other people's needs for using Virtualbox, but I have been using
KVM + virt-manager for almost a year now, coincidentally because I couldn't
get Virtualbox to run with the latest kernels (via jxself's repo).
Just some comments from my side on KVM + virt-manager:
- I use it primarily for headless servers.
- I've tested live distros in there. There is a known issue regarding sound.
There is also a workaround but apparently it might lead to security issues in
the VM. I don't know how serious this is, but I only did that long ago. I'm
not using the workaround now, so there's no sound, which is not an issue for
me at the moment.
- The virt-manager UI is unrefined compared to Virtualbox, but for me it
wasn't an issue.
- You need a CPU that supports virtualisation.
https://help.ubuntu.com/community/KVM might be a useful read.
