whoa! If you haven't played through it at least once, you may have some scares (with the expansion) at least a few times... although, to me, it wasn't really about that. I actually envy you for not having played through yet. If you really want scares though, try to do a hardcore run (i.e. you die and you can never use that character again. they are actually dead for all intensive purposes). me and a friend went through normal on hardcore for the first time and there were plenty of close calls and it was some of the funnest things to talk about afterwards about how often we almost died.
as for online, i can't say much about it, other than that if you play with decent people, it can be one of the funnest multiplayer games ever, but if you play with people you don't know you can get alot of jerks.
most often loot gets distributed evenly just based on if you could use it i guess. but it ultimately comes down to whether the person who picked it up first is willing to give it to you. as long as you play with people who just want to have fun there's good loot for everyone i think.