I've played Dark Souls on the PS3 for ~100 hours. I tend to play a little cautiously, so I'm probably not as far into the game as some others would be. What I can tell you from my game experience is the gamepad controls are very very well done. The game combat feels great.
I've been a PC gamer since I built my 386dx and original soundblaster card, so I feel I "get" what PC gaming is about. It may be sacrilege, but you really owe it to yourself to get an xbox controller for some of the newer games on PC. Dark Souls really is designed to work with a gamepad and it isn't the same game with KB/M because you are missing the feel of the combat. As bad as the KB/M feels (and yeah it could be better) with the controller it feels great. It's actually really nice to play games with the xbox controller for the games that work well with it.
As for the quality of the port - it is subjective due to the arguments around how much the game is changed to be more PC-friendly. I've played 10 hours or so and the game controls feel correct with the gamepad, and there are no glitches or crashes, and the performance is even more solid than on my PS3. Using the graphics fix works well which is a nice bonus, but the game as delivered from the developer is pretty solid.
Contrast this with a game like Dead Island, which makes my Nvidia 570GTX want to burst into flames after 10 minutes for no apparent reason. Now *that* is a bad port.
This game is one of those that will be on people's all-time favorite lists. People will be playing it 5 years from now. Make the investment in a gamepad, it will be worth it.
Seeing all these complaints is just strange to me. Play the game as it was designed and you will understand why people like it.