Big Mick beat me to it. I've experienced the same thing, lots of times. The acoustics of the room can make a profound difference in and of themselves; add in the effect of all those stringed instruments hanging around you, and the resonance in the shop can be delightful. Then you go home, sit on your overstuffed couch that rests on the deep-pile carpet next to the closed drapes, with the relative humidity up around 100 per cent, and the noise from the neighbors intruding -- it can be pretty disappointing at first blush. I agree with the guest who suggested bringing the same guitar back to the shop and playing it there again before trading it for another.