I recently started a playthrough using this mod for the first time in my game - I have probably 20 hours or so on the character, with her level about 10.
First of all, installing it is as easy as it gets. It's just one .esp file - extract the archive contents into your Fallout New Vegas\Data folder, then enable it in the Data Files section of the game launcher or in your mod manager. If this is the only mod you're using, that's all you need to do. You will need all of the DLCs though, including Gun Runner's Arsenal and Courier's Stash.
If you're using a number of mods, you should be using some kind of mod manager (and BOSS) anyway to properly install and sort them. Also a merged or a bashed patch if your load order is lengthy.
The next thing is that it's really intended for play in hardcoe mode. If you have hardcoe disabled, that takes away at least half the reason to play the mod. And when you're in hardcoe mode, you'll immediately notice that the hunger, thirst and sleep counters tick up much, much faster. You will have to eat and drink a lot to stay on top of those counters. Food and healing item drops from enemies are also severely reduced, and lots of Stimpaks in containers are replaced by Expired Stimpaks, which really svck. All stimpaks also have weight now. The Survival skill is your best friend with this mod.
The other immediately noticeable thing about the mod is that your encumbrance limit is reduced by a bunch - 50 pounds base instead of 150 pounds, with a 10 pound increase for each point you put into STR. I think there are backpacks and armor items with a backpack effect, which increase your carrying capacity, plus the perks like Strong Back are still there. Companion carry weights are also nerfed down to your value. You maximum hit points are also reduced by quite a bit. A lot of things in the game are tweaked - the readme included with the mod has a complete changelog of everything that is tweaked.
So far I don't find that it makes the game stupidly hard, but it does introduce a whole new set of challenges you have to deal with, and players whose combat style has been to charge head-on at enemies while spamming hot-keyed stimpaks will have to change those tactics, or die. A lot. Personally, I love it.
The best thing to do is what J.E. Sawyer himself says; install it, start a new game, and play with it for a while. If you don't like it, just delete it and move on.