I have been playing with the Passport Pro since the firmware update. . . . . with relatively small file transfers.
It SEEMS to be working as advertised. And it is reasonably plug and play (once you have it set up) I would advise you to “practice” your workflow in advance of the trip to make sure it is working out like you intended.
If I was you, I would pop the SD cards into the drive nightly to transfer files, and only reformat the card if it gets full. This way, if you LOSE a camera, you only loose a day’s worth of images, not a weeks worth.
My last major trip was before the current firmware. I ended up leaving the drive at home and bringing a proper laptop with me for data backup. Simple reason was that I needed a laptop for other things, and I was under some very tight space/weight constraints. The Wireless pro was left home in favor of bringing an additional camera lens. The answer for the next trip might involve bringing a Surface tablet in lieu of a heavier/larger laptop so I could bring the wireless pro.