Installing the Nitro is as simple as connecting it using the lengthy (185cm) white USB-to-miniUSB cable that comes in the box then installing the drivers from the included CD.
For the Nitro to work you must run the Firestorm software that comes on the CD. It's a simple program with just sliders on it for controlling engine (core clock), memory, shader, and fan speed and there's a temperature readout as well. Clicking the options button lets you choose whether to have Firestorm start when Windows starts up and if so whether to have it apply your overclocking settings straight away.
It's this need for Firestorm to be running that prevents the Nitro from being compatible with non-Zotac cards. If you try and run the software with any other nVidia card a warning message appears and when you click 'OK' the program closes. However, with a bit of experimentation, our friends over at bit-tech discovered that Firestorm can be forced to stay open by holding down the 'Shift' key when you click the 'OK' button on the warning message, enabling you to overclock any nVidia card (there's no joy for owners of ATI graphics cards though).
Incidentally, the Nitro is also compatible with surprisingly old cards, as well. Certainly cards as old as nVidia 7000 series will work.
The controls on the Nitro reflect those in Firestorm except there are only three buttons with which to control the whole lot. Consequently the buttons are context driven with the left most generally controlling which setting you're currently adjusting and the other two being used to increase or decrease the setting's value. There's also a profile system enabling you to switch between different sets of values at the touch of a button, which is great if, say, you only want your card overclocked when gaming.
For the most part it's a pretty simple system that is quick to master. However, there was one particular annoyance. If you're adjusting a setting but then leave the Nitro idle for five seconds (to look up at your screen to make sure no artefacts have been introduced to your game by your latest clock increase) it reverts back to the main menu. Being as one of the three options on the main menu is 'default', which sets all the clock speeds back to their original settings, if you're not careful you can inadvertently erase your work in progress.
This does highlight precisely what is so great about the Nitro, though. You can overclock your graphics card while running a game, enabling you to instantly see the effects of each tiny increase and allowing you to more accurately find the exact limit of your card's performance. If your game begins to show signs a corruption or even seems to crash, you can sometimes pull it back from the brink by dialing back the overclocking settings. It doesn't always work but it's better than what you can do with any other system of overclocking.
Obviously once you've found your optimal settings the Nitro holds no advantage over other software solutions like the profile manager in nVidia's drivers or the keyboard shortcuts available in Rivatuner. However, it makes the actual process of finding those settings infinitely easier.