You'll need 7-Zip to extract it. Other than that, just click SSP(.exe) and it will run. The mouselook can be enabled from the options before starting the game. It includes DOSBox.

It actually holds up rather well. It looks pretty damn good, partially because it also supports resolutions higher than 320x200, and the controls are probably more natural to a player today than in 1994. While pretty much all of the actions are performed with the mouse, similar to a point & click adventure, the movement works more or less as it does in shooters today, albeit more detailed.
S,Z,X and C work exactly like the typical WASD setup. A & D are addtionally there for turning. Q,W and E are for leaning from side to side. R,F,V control looking up and down. T,G,B are for standing up and crouching.
Seems excessive, but most of these are purely situational anyway and they're all grouped together, whereas other games would scatter their controls all over the keyboard.

The on-screen interface also looks more clunky and intimidating than it actually is. Most of it can be customized to some degree, or you can just switch to the "fullscreen" mode. Works reasonably well and I've had less issues with it than with the horrid UI of System Shock 2.
The atmosphere is also great. Probably not exactly scary these days, but still rather tense and creepy.

In general, I like it a lot more than the sequel and I don't have any nostalgic attachment to either game.

Fixed the momentary lapse of judgement.

Alright I tested it and the game works right out of the box. So my question.

When I quit the game it goes to DOSBox text saying, "Thank you for Playing System Shock 1"

And its stays there for awhile that I had to alt tab to have it in windowed more and press the X (Close) button to turn it off?

Is that how I truly turn it off or is there a more "safer" way?

Dude, that's just a message inside the emulated environment. You can just as well kill the DOSBox process at any point, it really makes no difference as long as you don't kill DOSBox while you're saving the game.

Alright then its just that I assume it would turn off on its own after I press "Quit Game"

You can type "exit", if you really want :P

In the meantime SYSTEMSHOCK Portable works fairly well from what I tested.

DOSBox has a command called exit. If you type exit and press enter, it should close DOSBox if it allows you to type.

That is what I meant by mods.

I'd love to see System Shock on here would buy day 1! :)

Alright now System Shock Portable cannot play for some reason:

I launch the game, I see the DOSBOx menu saying:

"Main Menu"

o: Options
i: Information
q:Quit

But the option to start the game is not there, it was above options and its gone?

What happens if you enter 'b'? That's the input that normally makes you start the game.
Yeah, as phaolo said, you can manually enter "exit" to quit DOSBox as well. GOG always appends that one to its DOSBoxed games, it's missing from SSP for some reason but it's really the only difference. You can make DOSBox automatically close itself the way GOG games do by editing the dosbox.conf in RES\dosbox. Just add a line that says "exit" at the end of the file and you're good.

no
downloading as we speak