I own a Lowepro Vertex 200 AW. Just big enough for all my gear (house+grip, 70-200, 24-105, 10-22, 2x, 3x580exII, transmitters, bunch of battery-packs, all the extras), a compartment for a laptop and a special mount outside for the tripod.
It's "just" a 200 but it's huge, there is a 300 version that is even bigger.
With all the gear packed it's really heavy.
Regardless if the straps are made for walking. It still takes a toll on your back.
If your in to the Runner 350 and your planing on traveling with all your gear I would recommend the Runner x350 AW where the x is wheels and grip as a trolley.
Then I would get a smaller one like the Slingshot 200 for some extra lenses/stuff and just have the camera around the neck while sightseeing and leave the gear that you don't need at the hotel.