Ive demo'd about 6 rackets now and I can tell you its a pretty frustrating experience. Most of the rackets come with cheap strings with tensions all over the map. Who knows how long those strings have been on there. Not to mention the grip sizes vary and they always give you the most slippery overgrip possible. The only benefit really is to feel the swingweight and how the racquet feels in your hand. Hitting the ball itself with a demo racket usually doesn't do the stick justice. Right now I am demo'ing the notorious dunlop AG 100. Quality stick from what I hear. Good reviews on TW and discounted price for 100 bucks is a plus. Anyways it has some cheap full poly on it. Its like hitting the ball with a piece of wood. Then I switch back to the yonex rqis 1 tour which was strung very loosely with a cheapy syn gut. The ball flies off my strings and feels like butter. I thought demo'ing rackets would help my decision but im still just going to guess and pray I get a racket that feels good for my game. I guess thats why people accumulate / sell so many rackets.