Its addictive, but very hard, its unforgiving but gets in your soul.
Game has a lot of grind, and you die lots in this game. Learn to ignore death and get into some sort of trance or this game will get you :). Need to be very patient and focused. You will most likely have to go through same levels many times, since the only mode in game - very hard. Its not just hard, its learning the game by dieing. Every new encounter will most likely result in your death, but next time you'll know what to do and probably won't die, probably. :)
Weak nerves, easily get frustrated, don't have patience - DON'T PLAY this game. This is one of the most brutal and unforgiving games I've ever played. It will get you by your nuts and will squeeze them every time you die lol :).
I give it 8.5, even though I'd easily give it 5. But this game shouldn't be compared or reviewed as other games out there. This game is one of a kind, sorta. The only similar game I've played before was Too Human. Demon's Souls however is much tougher and very long. If game wasn't so tough you'd be able to beat it in probably 6-8 hours.