Here is what I did.
1. Installed it under VMware as a virtual system running under the Windows 7 host - instruction how to are here
2. Activated it like a clean install - how to instructions are here
Now I can run both systems side by side and switch between them with one click. Nothing could be better. One of the VMware facilities is to share the clipboard. That makes it extremely easy to move files from one system to the other - just Copy from one system and Paste into the other system. External devices attach to whichever system is active. If e.g. you connect a USB stick to the PC whilst working in Windows 8, it will show up in Windows 8. If Windows 8 is not active, it will show up in Windows 7. Same for external disks, the cd reader, etc.
As to the question whether it is worth it: Windows 8 is an interesting system. It takes some getting used to but you can perform any Windows 7 task on it. There is not a lot more new function, but it runs faster than Win7. Since I am running my OS from a SSD, the performance difference is minimal though.
It comes with some interesting applications which, I guess, are mostly targetted at the tablet users. But they run well on the PC too.
Make sure you follow the instructions I linked by the letter. Then you will really enjoy it. My Win8 performance in virtual is the same as my Win7 performance on the real machine. But as I said, I run off a fast SSD and I have an i7 CPU and 8GB of RAM. I gave 4GB of RAM to the virtual machine, but 2 or 3GB should be OK too.