VirtualBox had been quite good until it repeatedly started restarting my host machine (!!) -- this only started happening recently, and as I understand it, the culprit is one of the many Active X controls that financial sites (in a land Renegade is familiar with) force on the user.
That got me to try out VMware player, and that didn't suffer the same problem.
However, if you do some searches you'll probably find that both VirtualBox and VMware products have had problems with some Active X controls. So my conclusion is to keep both handy - diversification may be our friend here.
I haven't heard of other major host-os-killing situations though, so perhaps you won't ever be effected