If the place smells like someone died in there, so much so that the neighbors call the cops....that's way too dirty. (Yes, I did know a dude this happened to.)
Yes, it's way too dirty long before that. I have no problem with disorganization. Papers everywhere in odd piles do not bother me. Closets out of order also do not bother me. But when we start talking about bacteria and mold collecting in your kitchen and bathroom for weeks on end, it's a problem. If I go into the guys bathroom and get the same feeling I get in a public (gas station) bathroom, then it's a problem. Dirty dishes from three weeks ago, garbage overflowing and STINK throughout the home are a problem.
I used to go to see my boyfriend on the weekends and while he was in class, I'd clean his place, just sos I could actually use the bathroom in peace.
OTOH, I don't like neat freaks. If you are vacuuming your floor while I am at your place for dinner, I probably won't be returning.