I do them regularly. Be sure to find a way to ask the sales associate to demonstrate all the targeted features, even battery and display for instance.
If you go when you think the store is least busy, that makes it quicker. Not a lot of narrative. Be sure to find a way to note everything talked about the target phone. At first, there is much to remember, but after practice it's not overwhelming.
Do not read so much, look about you and think of what you see there.
Richard Feynman-- letter to Ashok Arora, 4 January 1967, published in Perfectly Reasonable Deviations from the Beaten Track (2005) p. 230