The mufaletta I enjoyed was one delicious greasy concoction. The size of the sandwich is not huge but there is a good amount of meat and because of the grease it will fill you up, no prob. Don't be afraid of it.... It was way good with the olive salad immersing the sandwich with its salty goodness. Oh it reminds me of the various tempting food passages described in the food memoir Blood, Bones, and Butter.
I also tried three cured meats: the tuscan (ok but not quite to my liking - pork based), the saucisson sec (better than the tuscan - pork based), and a beef/pork stick (my favorite) that is perfect to eat as your walking.
The place is fun to walk into though it is a little pricier as one would expect. Give it a go, splurge a little on a special day and try a cured meat or sandwich or a fresh slice of meat to cook up back home.