jags,
I can't comment on these in particular, though they certainly do look very nice.
In general, lightweight panniers do sometimes require a bit more care to last as long as their more sturdily constructed, heavier brethren.
You wouldn't want to have sharp-pokey stuff inside, and I would imagine they might not fare the best in a sliding fall. I do see they have a pretty basic mounting arrangement (bungee and hooks) and it looks as if there might be no back stiffener, so some careful packing might be needed.
I know my Ortlieb Plus models weigh a lot with nothing in them, bur are sturdy as all get-out; the Cordura nylon outer shells are close to bombproof. I think lightweight panniers are a great way to save weight...but require greater care and may have a shorter lifespan. Horses for courses, really.
Best,
Dan.