What do you dislike most about looking for a rental? (apartment, roomie or house)?

I'm trying to figure out what problems or inconveniences people experience when looking for a rental; that is when looking for an apartment, a roommate or a house to rent. As a result how do you think you'd like to feel during the rental-seeking process? What things could be improved upon? Like what if you could get a sneak peek of what tenants live in an apartment building, or if you could read reviews or comments from tenants. Any opinions are greatly appreciated :)