Witcher III is a great game no doubt, but it isn't without its issues and bugs. The game is highly demanding on your system, my system runs very hot when playing at medium settings - something GTA V at Very High settings doesn't even do - this is how demanding Witcher 3 is on your system.
The story and quests are carefully crafted and you'll discover many interesting twists along its very long path, often leading the player into finding new side quests or contracts. Each town has a board which uncovers many explorable areas, these are the time consuming part of Witcher 3, of course you don' t have to do these but you'll be missing out on plenty of loot and gold.
The major issues with Witcher 3, besides the high system demands are fairly easy to describe, the swimming controls are fairly poor, the crossbow is fairly useless on land, but instantly kills monsters underwater.. and gwent is a major mess. Character movement also feels clunky, sometimes its nearly impossible to collect some loot because the game refuses to let you move close enough to an object. Horse combat is a mess too, even though you can kill most enemies in one hit on horse back, for the most part its just easier and quicker to jump off the horse and fight regularly.
Gwent needs plenty of rebalancing and patches to be really a viable source of fun, I'm sure other people could argue that but lets face facts, the developers messed up the Gwent mini-game - Its a source of major frustration, many AI players blatantly cheat and the outcome of the game more or less is decided before you even play, far too many peasants or basic gwent players have overpowered decks with multiple hero cards, which 'always' appear - where as, your best cards hardly ever appear. A gwent card seller mod needs to be created to bypass this terrible system.
The biggest concern is that the developers are going to sell Gwent DLC packs, because getting better gwent cards is nearly impossible, you get a few quests to face seasoned players which will award you with some better cards, but some of these matches again - are a frustrating mess when the AI throws out some nearly perfect card combinations, forcing the player to retry the match over and over again. Unfortunately, little strategy can be used because the AI uses far too many cheap tricks, making the whole mini-game far less fun, and more of an exercise in patience.
Pro
Highly immersive gameplay
Great Graphics
Many quests
Exploration is rewarded
Fun combat
good crafting system
Con
Swimming controls are awkward
Highly flawed gwent system
Heavy system resource demands
Buggy quests
Clunky movement system