Perhaps we are a bit on the "heavy givers" side of this discussion, but our reviews have been spectacular. The reviews are for the entire stay, so leaving something, does in my case, not necessitate special recognition in a review.
From a private welcome note, to a bottle of sparkling water and six sodas and local pre-packaged cookies, to a full line of bathroom amenities (soaps 3.0oz and hand soap 2.0oz, hotel size shampoo, conditioner, moisturizer and softener, as well as make up removal pads (save my towels...) and Q-Tips ($1.00 at the dollar store). In the Kitchen I have coffee and decaf, to be made (hot) chocolate packets as well as Quaker Oats (varieties). Of course for the cooking there is an assortment of spices.
In the Bedroom if it is known to be an anniversary or birthday we have a bottle of Champagne upon arrival with a personalized card congratulating the person/couple etc.
I used to provide individually wrapped slippers, but the cost become prohibitive, so I only occassionaly (arbitrary) hand them out.
These are ALL items that do not go bad if not used, but go a huge way to foster a "home away from home" feeling. We do get tons of returning guest. Perhaps it has do so do with some of the amenities we provide.
Best
Peter