At first you might think that is mostly the case from before. You pick up a skill and that is your spec path for the most part with a little branching possible later. Well not here in 1999 mode. You will make a choice at the beginning of the game and that will be your path to live with. You choose poorly and that could lead to "game over" real quickly. More or less you will be making choices that will permanently affect how you play the game and re-dos are they way of the dodo.
One example that has been given for this mode is thus: Say you choose to be highly skilled with pistols. You choose that path and that is what you get. You will end up being a bad ass, dead eye with pistols but gods help you if you run out of ammo and need to use secondary weapons.
On top of this feature in the 1999 mode, ammo and health will be so sparse that you will need to make everything count. That also includes "respawns." If you don't have the resources to purchase a respawn then it is truly game over and you have to start again. Well at least start again from where ever your last save was.
It does need to be known that this mode is not for all gamers out there and Irrational Games want to make sure you know it. In fact if you want to enable this mode you will have to dig through game settings to enable it. This was to ensure gamers who don't want to be punished this hard don't accidentally stumble on to the mode. It is for gamers who truly want to be punished and have the full challenge.
Now to me this is a brilliant addition to BioShock Infinite or really any game out there. Due to the nature of how games are distributed most of them really lack a lot of replay value. Especially FPS titles that don't focus on multiplayer and then single player. The 1999 mode will be something I can see adding some form of longevity to Infinite as I am sure that there will be so many purposed tactics to playing the game through on the mode. From the Plasmid combos to which weapons specs work the best down to specific tactics for every enemy encounter.
We'll see how this pans out though. It could be something added in that even the most hardcore of us find too taxing to spend time with. How many times can you go through failure before you finally say screw this I'm playing something else? That is at least after playing the game normally.