Difficult RPG but you feel like you make progress each time. Excellent design.
The difficulty comes from a few things; most enemies can rip you apart in seconds if you let your guard down, some enemies are particularly annoying (particularly in Shrine of Storms) and the terrain can sometimes lead to instant death pitfalls with no warning other than those a kindly online player may or may not have left (particularly in Latria). However the main factors of difficulty are three things:
1 - If you die you lose all your souls until you reach your bloodstain and every non-boss enemy respawns. If you die a second time all the souls you had are gone forever. This is why stockpiling souls is a mistake, it's a lot better to farm early content if you want something expensive.
2 - Healing items take a long time to eat, if you try to eat at the wrong moment during a fight the enemy could kill you three times over before you'll have finished the animation.
3 - Opening the menu doesn't pause the game. This is more something you just have to get used to, I strongly recommend farming 10 faith and the miracle Evacuate which lets you go back to the Nexus with all your souls at any time just in case you have to answer the phone.
Having said how hard the game is it is very important to note that although it is a hard game the enemies are all well balanced and once you recognise their attack pattern countering it is easy to do and once you get the hang of it you'll never have trouble with that particular enemy again unless they throw dozens at you.
Now onto other things. The soundtrack in the game is incredible. I can honestly say I'm struggling to think of a single game that does background music as well as Demon's Souls. The music is very varied, one suitably intimidating boss has ominous chanting as his music while another has a fast paced tune occassionally bursting into heavy percussion, again well suited to this boss who attacks rather predictably for the most part then suddenly launches a rather nasty fireball salvo or two.
As for the graphics, this time I can't say that I'm struggling to think of a game that does graphics as well as Demon's Souls, I'm sure Final Fantasy 13 for example easily has it beat. However this is because modern games are all about graphics and having a truly brilliant soundtrack is something much more rare. The graphics of Demon's Souls are fantastic and effective, sometimes hauntingly so, particularly in the Prison of Hope. The sight of bloodstained torture chambers, iron maidens and tiny cells mixed with the always closeby sound of the chiming of the bells the illithid-esque prison guards wear will at the very least match the atmosphere of any of the most popular survival horror titles.
Now onto controls and our UI. Our d pad selects weapons/shields (both weapons and shields take up the same slot, giving the undeniably awesome but incredibly useless option of dual weilding shields) with the left and right arrow buttons, spells and miracles with the up arrow and consumable items with the down arrow. 2 weapons or shields can be put in both the left and right button slots and 5 consumable items can be put in the down slot. The number of spells or miracles that can be equipped increases as you level intelligence and faith respectively. To use magic a catalyst must be equipped and to use miracles a talisman must be equipped. Circle is our dodge button and triangle alternates between dual weilding the right and left hand items or two hand weilding the right hand item, obviously giving increased attack power but compromised defence.
To conclude Demon's Souls is a wonderfully atmospheric gem of a game, it will hurt you and frustrate you but you'll forgive it because its good points, for myself at least, make me feel that with each death I progress further and further and you will never quite stop having fun.