We use ours a lot for access to the roof (as you might expect) - actually Sally was up there today polishing the moon roof.
We've carried a shovel, empty jerrycans and water containers, folding bikes and other stuff on the roof - only fairly light stuff though.
We also use it to strap the grey water tank to, as seen above - yes, our little camper doesn't have a built in tank, just some rubber hose hanging from the sink outlet (actually it is a bike inner tube :))
Plus the rather battered flag is cable-tied to the ladder, as is one of the stainless steel shelves from a Dometic RM2410, which normally sits upright against the ladder, but I can drop it down on an old bit of chain (which I think was once part of a horse lead) into horizontal position to rest drinks and other things being passed between the outside and the camper.
As you can see from the above picture the bottom step of the ladder is far too high to reach from the ground - the technique is to climb up into the camper, face outwards and put your left foot on the frame that attaches the ladder to the camper and swing up to get your right foot on the first step. Fortunately the roof rails I fitted ensure there is plenty to grab hold of when transitioning from the ladder onto the actual roof - I wouldn't want to do it if all I had up there was a smooth roof with nothing to pull myself onto it with.
Steve.