It's basically 'just right' for me. Screw up and you're dead, but you can kill stuff without 'cheating' or 'exploiting' provided you know what you're doing.
I agree. I've played on Master since the start and it's generally a nice difficulty. I ran into problems in the 20's where it actually did get too easy, but I play a Sneak/Archer so it's easy to snipe and avoid direct combat when I need to. Most of the time anyway, Dragons and bosses are different. To make it even harder I levelled a lot of non-combat skills and now it's really nice and challenging even while sniping. I imagine Master is pretty hard for melee characters.