I like Katz's because it's close to my office when I need my fix of cured beef and hot mustard.
It's my opinion that they could improve on their menu by allowing a choice of size (it seems their sandwiches only come in one, large size). Also, I do enjoy being able to request what fat level I receive on my sandwich. Perhaps they allow it here, but I've heard otherwise (reviews below). I also agree they could source a better baker for their buns as they're commonly dry.
But who am I to argue with an establishment with such longevity as Katz's?
I really don't have much to add to the other reviews but I had to get a deli review under my belt if only to share a Hedbergism:
"I hate sandwiches at New York delis, too much fuckin' meat on the sandwich. It's like a cow with a cracker on either side. "What would you like sir?" "A pastrami sandwich." "Anything else?" "Yeah, a loaf of bread and some other people."
~ Mitch Hedberg
:)