Has any tried out Hard or even the most difficult setting (is it called insane?)

I just started last night and I thought the enemies were too easy and thus felt too arcadey.

How much harder are the other settings, do you die much?

I started on normal.. but I think I am going to just start over on nightmare for the challenge when i get off work. I am curious how hard it is though.

I started on hard, the enemies die fairly quick, and with how fast you regen and the defib thing it seems fairly easy, though I just reached Wellsprings so we will see as I progress.