Dirty Room & Surly Staff
I stayed at the Sheraton Philadelphia Downtown Hotel for 4 nights in May 2012 and will not return. 
Upon entry to my room, I noticed that the carpet was quite dirty. That's understandable, considering it is a beige carpet that I am sure gets plenty of traffic. What is not understandable is how dirty the bathroom floor and walls were. I immediately noticed black dirt marks all over the floor. The next morning, I noticed the same black dirt marks while I was in the shower. I notified the front desk in person of the dirty bathroom and asked that the floors and walls be cleaned. I also left a monetary tip for the maid each day. Despite numerous requests, the bathroom floor and walls were never cleaned during my stay. Very disgusting. Most (not all) of the front desk staff were also rude and surly during my interactions with them. The hotel AC (and heater) is a wall unit that you typically see in a motel. It is very noisy and blows the dirt and dust in the room around. The hairdryer was also coated in dirt and dust.
I will mention the few positives: the bed was very comfortable, the shower had great water pressure and the tv was great. 
Had the entire city of Philadelphia not been sold out during the week of my stay, I would have switched hotels after my first night. Management gives canned responses to complaints: "Thank you for your comments. It's how we can improve." Obviously there is no intent to improve if the majority of guests provide the same comments. Oh, and I am a loyal SPGer who won't be loyal to this property.