Yes I use virtualbox to try different OS, and also for practical reasons- sometimes I need to use window apps like IE and I don't want to boot into windows. But as of the last two or so versions of Ubuntu virtualbox wasn't working properly- the guest OS often freezes and the virtualbox service itself hangs. I hope it would function properly on opernSUSE.
I agree, virtualbox is good for beginners.
I also use it because its easy....and it doesn't cost $20/year like VMWare.
I notice that for desktop virtualisation, vbox runs very well on .... windoze.
For Linux, I recommend running headless. So, after you have your guest running the way you like. Shut it down and run it headless. Configure the display to allow RDC (remote desktop) and choose a port like 5001 for your first VM 5002 for your next...Don't use the default unless you only have one machine.
vboxmanage startvm ubuntu10 --type headless
Then to power it down:
vboxmanage controlvm ubuntu10 acpipowerbutton
For stability, you can try VMWare Hypervisor bare metal. But you can look into that later.