I rode almost 1,000 miles from Amsterdam to Brest with this rig (Blackburn Outpost) and am happy with how will it worked. The downsides to this type of luggage is that it would take a lot of time to pack because everything had to be in its spot to work comfortably, whereas with panniers it's quicker and easier to chuck stuff in and go. For instance, I had to pack the frame bag carefully so it didn't bulge and rub against my legs. The only issue I had with the seat bag is that it would sway a bit when I pedaled out of the saddle. The whole system is very secure and waterproof. I stupidly crashed in The Hague on day 1 thinking I was a bikepacking Tom Pidcock and absolutely nothing shook loose after a pretty violent impact. With the HB Roll, I added a Voile ski strap for extra security and it was immovable and everything stayed perfectly in place. The pop on and off system is really convenient as it fit well between the drops of my 42cm drop bars. I had to ditch the dry bag it comes with because it would have been just too wide.
Compared to panniers, I found it easier to move through crowds and get aboard ferries and trains without the extra width. I'd also say it was all easy to pack in a bike box for air travel.
by Qaintstr8inline