Was looking for ways in which to make my rogue / cleric gestalt more effective, while doing so got to thinking about the stone shape spell. Standard action to use and instantaneous effect, so my thinking is whats to stop you from readying the spell against an oncoming creature and using the spell to form an instant 10 ft long stone spike angled to set against its attack, or readying it against a volley of arrows you know is coming into the form of a tower shield or small wall etc, another might be to sneak up to a creature and drop it into a 10ft pit. If these kinds of things can be done there are many others.
Before i spring this on my DM looking to see if there is any reasons against such uses.
I don't see anything particularly wrong with using it that way but I don't think it was ever intended to be used as a reactionary spell. For a rogue/cleric I would think you would use it to bypass traps and door mostly. Form a bridge over an existing pit, make your own door to bypass a tough lock, disable a trap without having to make a roll. Those sort of things but that's just my opinion.