I thought this article from Punch Jump hit the nail on the head. Demon’s Souls breaks the normal chains of gaming convention.
The most important part of Demon’s Souls is that the game’s no-save policy, clever enemies, and traps all coincide in a masterful design that allows the player to learn with each level attempt. Much like a classic 2D side-scroller, users will learn to defeat known enemies quicker, avoid traps, and become accustomed to the no-save policy.
I haven’t gotten to log much time with the game yet; hopefully have some time over the weekend. The user views on the game are starting to roll into Metacritic. Demon’s Souls is still rated at 90% (based 33 critic reviews), but perhaps most important is the 9.4 user score (based on 87 votes).