The caveat is that I think Demon's Souls is the best game ever. So, Dark Souls is still very excellent. It has a lot going for it that on paper are improvements over Demon's Souls, like a larger and more diverse environment and even color pallet, but there is a distinct lack of fine tuning and perfect craftsmanship present in the level design and mechanics that Demon's Souls had in abundance. Dark Souls occasionally will rely on enemies that exploit frame rate or camera issues, and sometimes will make bosses difficult simply by giving them a great deal of hitpoints. Furthermore, the notion of an Open World is highly dubious, since the game makes it clear which of the three paths are realistically open to a starting player at the beginning of the game, the other two being virtually impossible. (A note: to enhance this experience it is paramount to choose the Master Key as your starting item. It just opens up a few extra paths at the beginning.)

Again, all these issues aside, Dark Souls should be played by absolutely everyone with even particle of interest in video games. It is still among the best the entire medium can and will ever offer.