The main problem with Guest House is the lack of likable characters. Everyone is mean spirited for most of the film. Even Pauly Shore. I like Pauly when he plays a nice guy / silly stoner. The film does take a kinder tone towards the end, but by then, it is too little too late.
I did laugh a few times. There is a fair amount of nudity and drug use, so not all is awful. Billy Zane looks intense in a sorta funny supporting role, and I believe Steve-O is even more insane when he is off drugs.
As for the plot, do you really care? I did notice some holes they forgot to cover. Guest House isn’t unwatchable, but I am quickly going to forget most of it.