Deus Ex is one of the best PC games in history, but even it isn't without its faults and shortcomings. Shifter addresses these and then some. Unused game content, buggy scripted events, several completely useless items, and certain design choices that can only be described as "annoying", all fixed (or at least "improved") by this little mod. I started Shifter in 2002 to fix just one of the latter -- the fact that weapons equipped with a laser sight won't turn it on automatically -- and the project has expanded exponentially since then. A few new weapons, some additional uses for existing items, new augmentations, and several fixes for existing Deus Ex bugs all exist in Shifter, along with a new multiplayer component. The mod is so popular it's been featured in Game Informer's July 2007 edition of Mod World; how many Deus Ex mods can say that? (only 3, to be specific) Shifter: "Removing the suck from Deus Ex" since 2002.
Shifter is a very well written mod both in planning and execution. It has kept Deus Ex relevant and modern looking since 2007.
From the outset you see new higher res textures and models of objects like cans, canisters, and loot-able garbage cans. Need some Zyme?
You may or may not like the new principle characters' models, I find Anna's and Gunther's a little too different from stock, but you will notice a large increase in character fidelity, enough to make reverting a model pointless.
A couple of quests have been fixed so that you can go ahead and do your thing without fear of having uncompleted quests. That is good for those of us who obsess over such things.
A little later on you will start to see restored content cut from the production release. This content melds perfectly with the game whether from the Shifter developer's efforts, Ion Storm's excellent work or both.
Some basic exploits are disabled, like lock picking, inventory mismanagement and xp gain to remove temptation for those of us who must exploit a loophole.
Shifter to Deus Ex stock looks a bit like HL1 Source to HL1 but it improves far more than just the background textures. The water is not Source engine level though, maybe that will be added in a future release.