If I was to pick a poster child for everything that could go wrong with porting a console game to PC, Dark Souls Prepare to Die would be it. And yet, the game itself is terrific. So, if you are considering buying this game, there a few important things you need to know.
First, it requires GFWL and rumor has it, although there has been no official statement, that GFWL will be closing as of July 2014. If the developers do not patch this out, your game might become useless after that point. However, Namco Bandai has stated that they will continue their support, so it's a wait and see what form that might take.
Update: The game was converted to Steamworks in Dec 2014. See Game Issues below.
Secondly, Dark Souls is a console port and the developers clearly stated that they were inexperienced with porting to pc. The pc version reflects that inexperience and needs several user mods to fix the problems. However, fans of the game begged for a PC version and the developers did their best in the time allotted. Once you get past the problems of getting it set up, there is nothing wrong with the actual game.
Thirdly, this game is punishing. It is one of the most challenging and frustrating games I have played. It is, however, also quite unique and intriguing.
Dark Souls is intense to say the least. In the beginning, it can be very hard and very frustrating until you get some practice on how to play and obtain some upgrades. You are punished severely for dying, and you will die often, and will have to play entire segments over and over again. If you do not enjoy this type of challenge, you would be wise to stay clear. The game does no hand holding, there are no ingame tutorials, except for a few controls in the beginning, there are no maps and no real indications of where to go when, except for some hints through dialogue with NPCs. There are, however, vast amounts of information given online with lots and lots of things you need to know. Fortunately, you can alt-tab out of the game to look things up as you go, but it's easy to misstep as there are few barriers to going into areas too advanced for your level. Also some people make the mistake of killing NPCs that can affect other things in the game.
Although there are several classes to choose from at the start with differing beginning stats, this will not hinder you from changing tactics later. However, the skill points are limited, so you should decide at some point which way to go. Weapon and armor stats and how they are affected are quite convoluted with no ingame help, so either look these up or try experimenting. This is not a run and gun game. Generally, trying to bully your way through fights will get you killed. Slow, steady and patient wins the day and you must learn the weaknesses of enemy types as well as your own vulnerabilities. The AI are not pushovers.
There is no quicksave and the game utilizes a checkpoint saving system in the form of lit bonfires. Although you lose humanity and soul currency if you die, you revive at the latest bonfire you rested at and can return to where you died to pick up your stuff as long as you don't die again before doing this. However, if you quit the game, you will restart at exactly the point where you quit. I would advise backing up your saves. Unfortunately, all the enemies respawn with the exception of the bosses. Bosses are very hard and there's lots of them, so you have to look for tactical ways to beat them.
Multiplayer and co-op are integrated into the game and are not separate modes, making this game quite unique. But this causes its own problems when people don't like or want to be invaded. Being hollow or human while playing online, determines whether you can be invaded by other players. You also need to be human to summon others for help. Unfortunately, you will meet twinkers and cheaters, but even honest invasions can get pretty annoying when you are trying to reach and kill bosses. Once the area boss is dead, you can't be invaded in that area regardless of your status. It is pretty cool to see phantoms of real players running through your game. You can play offline, but will not see the messages or players in this case. However, you can still summon help from NPCs for certain bosses.
I used the community made mouse fixes, but still had to do a lot of fiddling around with getting proper mouse and keyboard bindings as the game hints are all given in controller form. Controls in dsmfix.ini override the ingame controls for some actions so you don't have to worry about binding those. But you will have to experiment if you are going to use the mods. The game is perfectly playable with the keyboard and mouse, but using a controller will fine tune some movements.
I've given you all the bad news first, but this game, if it fits your tastes, is really quite amazing. There are several classes, upgrade choices and covenants that give perks, although most of these are for multiplayer. One of the great things is the almost unlimited variety and combinations of weapons and armour without feeling overwhelmed by it. You can really personalize your character and feel like it's all yours.
The visuals are not the best for a game of this age, but very suitable for a game of this style. Almost medieval in looks, buildings give the impression of vast age and dereliction. The graphics were certainly not optimized for the PC.
After you finish the game, you can play New game + retaining most of your equipment. You can continue to level up, but multiplayer has level parameters for summoning and invading.
Dark souls 2 makes some fundamental changes in the gameplay, so of course there is the usual debate of which one is better. One of those changes is not being able to stop invasions without playing offline or disconnecting your internet before starting the game. If you disconnect ingame, you may get banned.