As long as you 1 don't pay full price for this game and 2 don't expect AAA quality then you'll enjoy this game.
I started on the hardest difficulty but the only thing hard about the difficulty is finding the mission objectives.... The enemies aren't hard, they're incredibly dumb and if you keep repositioning you can just constantly outflank them as they'll fixate on the last known location they saw or heard you from. This was actually rather fun just outflanking and setting traps constantly. The downside though you pretty much have to give yourself the handicaps as even on the hardest difficulty you can run around like rambo just killing them with ease provided you know where they are and have the ammo, ammo is scarce on the harder difficulties. Any lower difficulty and the game is a joke, xray vision tagging of enemies, not that you even need that as the enemy locations are shown on your minimap including which direction they're facing so you don't even have to tag them to know where they are or where they're looking. You also get more xp for killing tagged enemies so you're loosing out if you don't tag them but want to give yourself a handicap but then again if you're playing on the Authentic difficulties XP doesn't do anything for you.
The other small gripe I have is the gravity bullet ballistics. The gravity is turned up to 11 or perhaps they got the scale wrong, enemies that are 100m away you'll need to adjust for bullet drop but then as this is a sniping game I can easily live with this but there is certainly an adjustment period where enemies look close and you wouldn't think you would have to adjust for wind or gravity but you do.
Positives:
Large open world style maps
Many enemies
Different types of enemies
Multiple traps and gadgets
Negatives:
Incredibly stupid AI although I'm tempted to put this into the positive as I had a lot of fun constantly flanking them
The sprinting is just wrong, it's clunky and awful
Overall slight clunkyness to the movement
The heart beat sound every time you scope in...
The perks (upgrades) you get don't work in Authentic difficulties but then again that does make sense just means whilst levelling up and unlocking them if playing on the harder difficulties is pointless.
Story is dull but who plays these titles for the story anyway
Some minor graphical problems like water looking terrible
I also have an issue where I have to launch the game twice, first time I launch I get screen tearing and second time it works perfectly, I also can't alt tab back into the game and have to kill it from task manager
I can recommend this game whilst bought on sale and heavily discounted, I paid $17 for it and it's easily worth that. Full price I would say ABSOLUTELY NOT.