Re: Sounds good but...
The clever bit about the Atlantis software (when I looked at it in anger a year or so ago after seeing it at VMworld anyway) was that it did two things to take the load off of backend disk - firstly, it did full deduped RAM caching of disk blocks in the VMhost RAM, (for both read and write) - the dedupe making it very efficient as most of the OS image hot blocks are common.
Secondly, it did dedupe, serialisation and compression of any writes back to disk, using an "inline" virtual NFS store - basically it shows your VMhost an NFS share (which live sin memory), where you provision your VMDK's as normal, but that NFS actually lives on an Atlantis VM on each host, which is then synced back to the underlying disk.
The idea is you should use the Atlantis provisioned storage for your VDI boot images and working drives, and stick your "proper" data on more traditional storage (file server or NAS or whatever), giving your very fast desktops with reliable file storage.
There's a good writeup of the new release (with comments input from the Atlantis guys) on Brianmadden.com if you want more detail. They've solved the persistant VDI image restriction, and it now supports multiple hypervisors etc. Nice that its licensed per desktop, and I reckon a per host version for server VM accelerationis forthcoming soon...