The VM is easily vulnerable to the host OS, so running in a VM only protects the activities you do in the VM in the sense that the software pwning the host might not be looking for it. So not really.
Unless you are not using the host OS for anything _other_ than virtualization. If the host OS is used to host VMs[1], which are then used for specific tasks (casual browsing, banking, development, etc). Any exploit will be limited to the VM. This would be a pretty solid setup. It is only vulnerable to attackers that have direct access to the hardware, or have the ability to exploit the hypervisor.
[1] in other words if the host OS is used as a hypervisor, or if the host OS _is_ a hypervisor.
