For me, I dislike placing a water bladder into my pack. After you drink up most of the water, things invariably shift around and sometimes you end up almost having to repack. It's not like you can just slip a bulging bladder into your pack. Good luck doing all that in the rain. As for leaving the bladder inside and refilling per the video -- I don't see the mere force of gravity being able to fill your bladder to bulging -- pushing all other contents out of the way...
I use two 1-liter size bladders -- one on each of the two side pockets of my pack. But I too like the idea of "hands free" hydration. Well, I can achieve exactly the same by simply connecting one of the bottles to my Platypus hydration tube -- with an Aquamira Frontier Pro in-line filter. The one thing I do have to do -- which I don't find onerous at all -- is that after finishing 1 liter -- I need to switch out the empty bladder with a full one (the one in the other side pocket). Takes about a minute (or less). And still a lot easier than opening up the pack, etc. as described above with an in-pack bladder.
Some people might ask whether I feel any imbalance as one bottle gets emptied while the other remains full. In all honesty -- I cannot tell the difference --not even a little bit. Which shouldn't be surprising since we are talking about 1-2 lbs. out of a total pack weight of 20 or so -- and most of it nicely centered!
Other advantages of placing the water bladders outside:
1. No worries about bladder leakage soaking your gear (or worse, sleep bag).
2. You can tell how much water you still have by sight or by feel.
3. It's easy to pull bladders out of side pockets for refill (no need to bring the entire pack down to the stream or to repack a bulging bladder into the pack).
4. Everything being equal, using the side pockets instead of internal pouch means you can get away with a smaller and lighter backpack.