Are there some other core VirtualBox features I'm not aware of that keep people pinned to it?
Its support for passing USB devices through to guests is pretty good. I have a Gentoo VM on a Win7 box for the sole purpose of continuing to use a scanner that the manufacturer doesn't support on Win7. The only area where it's let me down in the past was with trying to mess with iPhone firmware (such as for jailbreaking) from a Windows VM on a Linux host...don't know if it was something weird Apple was doing with USB or something else. Have other virtualization options caught up with this?
Also, VirtualBox console windows are less of a hassle to deal with than VMware console windows. Even with their respective guest addons installed and active, VMware is still enough of an annoyance that I'd rather RDP or SSH into the VM in question. (In fairness, VirtualBox is running locally, while the VMware VMs are on a couple of ESXi 5.x boxes accessed through vSphere...maybe their desktop virtualization tools, which I've not used in eons, are better.)