It's more a replacement for VMWare Server than VMWare ESX.
I think KVM/Xen are closer to ESX. VirtualBox ships with a webservice that you can write custom front-ends against (or script against).
Most of the VM tools seems to miss an ability to branch a VM (i.e. take a snapshot and break it off as a seperate instance). This would be hugely useful for installer testing.
Comments
It's more a replacement for VMWare Server than VMWare ESX. I think KVM/Xen are closer to ESX. VirtualBox ships with a webservice that you can write custom front-ends against (or script against).
Most of the VM tools seems to miss an ability to branch a VM (i.e. take a snapshot and break it off as a seperate instance). This would be hugely useful for installer testing.
I'm pretty sure that Virtualbox machines can be cloned, and they'll clone the latest snapshot. It's not easily exposed in the GUI though.