Do you not still license based on CPU, not what is on the machine?  So instead of 24 hours dev, 24 test, you might swap.  Only one up at a time, the machine is what is licensed.    You could do the same thing using backups if it were time effective.

We also use VMWare internally for Oracle development systems, demos (we keep a "shelf" of demos that we can start up, demo, then shut down), and for additional desktops to support multiple VPN clients (since different VPNs don't necessarily like each other much on Windows). As was mentioned here, we wouldn't use it for production (and like Mark said--who really knows how to license it properly), but love it for development. 

 ...this insinuates you don't see the need to properly license Oracle for development purposes. Am I missing something?