The on again/off again relationship between Survival and a burst DPS cooldown is once again off, and probably for good this time.
— Celestalon (@Celestalon) July 23, 2014
Right now it’s too soon to tell if it’s worth hanging onto stacks versus firing as soon as you get one. A lot will depend on how much Multistrike you have, and how quickly you generate those stacks.
Once Blizzard starts doing a numbers pass there will probably be some usage guidelines established, and maybe even an addon to tell you what to do, which as Delerium points out, “Blizzard won’t like so they’ll change the mechanic”.
I haven’t played enough Survival to get a good feel for it yet. Between pooling Lock and Load stacks, managing Focus and Serpent Sting, there may be enough complexity to make up for the lack of buttons.