The whole watch is very solid, and feels very good on the wrist, with no rattle at all. The locking switch also feels solid; you don't really notice it. It does take some getting used to the lack of "regular" chrono pushers, but I think that people will generally be pleasantly surprised by the heft and feel of the watch.
Note as well that there will be titanium, and platinum versions of the watch. This should make the locking switch less noticeable.