Since the "Real" keys are supposed to be pretty rare and uncommon it's not a big deal, plus all your character info is stored client-side so if people wanna cheat they can. The actual preorder guns you get (Gearbox guns) are things you'll replace by level 2, they're completely terrible level 1 newbie guns. The "Vault hunter's relic" you'll use for a bit simply because you won't have a relic that early in the game otherwise, but it only gives you a +5% chance at finding better loot so it's not hugely game breaking either. The biggest preorder reward is the mechromancer class which is due in a month or whatever.
Played up to level... Something. 13th I think. Fought a bunch of robots. Fought cars. Fought jet things. Shot many guns, had some good guns, guns starting to get weak compared to what we're facing. Could do with some upgrades soon. Buddy switched to being a gunzerker since he fucked up his save due some hilarious panic, game reinstalling, and choosing to use cloud save when he shouldn't have since he quit when Steam was down for like 5 minutes. Gunzerker seems way more powerful than siren or assassin, so I respecced to healer to support him more since he's kicking out most of the dakka.
Steam says 9 hours played now which seems a bit high but maybe I was going nuts, but it's quite good. Seems like Borderlands only improved. The weapon variation might be a hair less than I thought previously. There are the large differences between manufacturers and weapon type, but two guns of the same make and model are pretty similar. Seems to be less graphical changes to the models overall. Maybe. I've noticed a few almost identical models with different coloration, which was a rarer occurrence in the first game.
ALSO, enemies are way better in this. Not only more variety, the generic psychos and shit react a bit better. Slightly better at rolling to cover, avoiding fire, and reacting to being shot. And as mentioned there's a bit more variety in the enemies now, like psychos with flamethrowers, WAY more suicide psychos, some big burly guns akimbo guys who berserk and attack EVERYTHING if you shoot their helmets off, etc. Good stuff.