Visual Studio doesn't seem to run correctly in VirtualBox 5 and keep causing my Windows 8.1 guest OS to restart. I'm not certain this is because of VirtualBox 5, but the issue seems to have only happened after the update. I'm reverting back to VirtualBox 4.3.x by downloading it from here.
If you are running OS X El Capitan (10.11) and VirtualBox doesn't detect any USB devices, this is because Apple changed some security settings and VirtualBox 4 (even the current release,) hasn't caught up.
You can fix this easily by going to Oracle and downloading and installing the new VirtualBox 5. VirtualBox 4 won't detect the version 5 update, so you have to download it from Oracle. Some people recommend using the VirtualBox_Uninstall.tool to uninstall version 4.x, however I just installed VirtualBox 5 without uninstalling version 4.x and everything seems to be working fine.
Once you have installed VirtualBox and the extension pack, you will have full control of your USB devices again, including support for USB 3.0 devices.