I got a couple demos from these guys. The process of obtaining the demos was quick and easy.
The person at the store had excellent advice about rackets that I might like. The demo rackets were strung really well with high quality string. This last point is really important.
I had tried demos at other places, but the strings were so bad that I came away with a poor impression of the racket.

When I mentioned Racket String Workshop to my tennis friends, they all already knew of it and said it was by far the best pro shop in town. I guess I am late to the game, but am a big fan now!