Rotopax is the real deal, lots of guys out here run them. The only issue I've seen was one laying down on a roof rack in the sun, it swelled up and took some work to unlatch it.
ADV Rider guys use the small ones all the time and they stand up to repeated crashes and horrible vibration and shock. The midsize ones are popular with ATV guys, and the large ones I see on overland rigs on really nasty terrain.
They are a good product, but I stick with NATO cans for fuel and Scepter cans for water because I can carry more volume for the money.