With current systems, there's little to worry about with hardware compatibility. Those devices, such as old printers, can easily be shared into a VM for use. VM apps have come a long way in the last couple of years.
You could be right, that's why i said
"When Windows 7 first came out, some programs and devices did not work for me with x64 but did work with x86. That is why i decided to use dual-boot on this HTPC."
In addition to that, multi-boot systems require boot loaders on the drive...meaning if one messes up, you likely won't be able to boot the system at all. Once you run a repair, your other OSes won't be bootable, either.
This is not true.
I am on a dual boot pc now and there is no multi OS boot loader.
OS boot selection is done with the "One Time Boot Up" option (F12 for me).
Also, I have run repair on a multi boot PC with a multi OS boot loader, and all OS's worked afterwords.
With Windows 7, there's no need to test x86 vs x64 anymore. Maybe with Vista, yes, but those days are long gone. All you do is waste a license and drive space by multi-booting the same OS. Testing is a perfect reason to virtualize, because you can build a clean VM, and back it up. Then, after testing something, rolling back takes 1-2 minutes. That's it. Same with a system restore. Again, no boot loaders to mess with.
Could be there's no need today - i answered that above.
It's my understanding a separate license is needed for each OS irregardless if it is in a VM or stand alone.
Am i wrong with that understanding?
Can i legally install Windows OS in a VM and not need a different license for the VM OS than the Host OS license?
A functioning VM is a full working computer. There's no need for varying confidence levels. It has access to your host system's hardware.
The possibility of a "VM OS" causing a particular problem is eliminated.
I'm not sure what you mean by this, but VMs are isolated, in the sense that if one has an issue, it doesn't have any effect on the host system. That's the reason why virtualization has replaced multi-booting. If a VM does develop an issue, you can remove it or restore it from a backup with absolutely no effect on the host OS.
This simply means if i have a problem and I'm using a VM OS how can i be 100% guaranteed that the VM is not causing the issue.
With a stand alone OS, a VM is eliminated as a possible cause of the problem.