behave just like a "real" machine, at least they should do.
They have the same functionality as a regular machine and are just as vulnerable to problems.
As to your last question, It would be better to just not install Windows 7 RC at all. But that's just my opinion.
I was watching the video on Cnet TV about running windows 7 RC on a free virtual machine, Virtualbox. I've never used a virtual machine before so I was wondering if you can save files that you make on the vm or if the vm is read only. Would it be better to just install Windows 7 RC on bootcamp?