I have been touring (sealed road only) around Australia on my Monster 1100S for a few years and I'm loving it.
I really should have bought a Multistrada but I can't stand the look.
With bar raisers and properly sorted suspension, the bike is comfortable for long distance. Stock the Monster 1100S is way too stiff and quite uncomfortable on less than perect roads.
Fuel range wise, I get between 300-325kms before empty which is on par with what my friends on Multi 1200 get.
I've got the model without ABS, so my tank is slightly larger at 15L (tank capacity is reduced to 13.5L for M696/796/1100 with ABS).
Luggage wise, side panniers give you 2x14L, Tail bag 18L and tank bag another 14L. More than enough space to carry gear for a couple of weeks.
The Monster is the jack of all trades and if there is a will there is a way. After all, in Tassie I have met people touring Australia on Postie bikes (Honda CT110)!!