In-store testing is a good thing, but remember that many times "in store" is far from "real world". One important aspect for example, there is no wind in the store, and the floor is hard and level. This is part of the reason why Gitzos are so expensive. Unless you have felt one, it's hard to describe but even after its fully extended and set up, they are still solid. No flex in the leg, even along the joints. This makes it hold up a lot better than some cheaper/lighter tripods, and that is where some of the monetary difference lies. Almost anything will hold a camera steady in a room with a solid floor and no wind, but once you get out into adverse conditions, the quality of the tripod will determine when you pack it in and go home.
Ruahrc