I am going to second R0bR's suggestion to use VHD native boot. It is going to be the safest way to try out Windows 8 in what is essentially a bare-metal install.

To answer an earlier question, regarding whether it's worth upgrading, I am going to say yes. You will need to make some adjustments, with regards to the Windows 8 UI. That is a given. You can learn to use it in various ways, or you can just take every tile off except for the desktop and work more or less exclusively in the Desktop UI. Windows 8 does have some under the hood improvements with regards to security, speed, and stability that make it worth it in my opinion.

One thing you do not have to worry about, though, is needing to upgrade in order to have a supported system. Windows 7 will receive security updates through 2020.