Blu-ray burn speed?

How long would it take to rip a blu-ray using this?

http://www.ebay.com/itm/White-USB-External-Blu-ray-rom-drive-w-Lightscribe-DVD-Burner-4x-BD-ROM-TS-LB23L-/230733903690#vi-content

Would it even be worth it or would I be better off getting an internal drive?