Currently level 16 on Zer0, god please don't ever, ever change the difficulty. I hope they make enough money that they don't feel the need to Blizzardize it, and I don't feel they will. Gearbox is comfortable with how they make games.
I die, sure, but I always come through and win. Haven't played Co-op yet, but I will on my next playthrough. Love sniper rifles still, headshots everywhere. I've found sniper rifle + fire pistol + shield SMG to be my usual lineup right now, but it changes (not the rifle) based on how I need to play.