There are some things that I think need some eh... calibrations.
I sort them out in matter of importance for me.
MOST IMPORTANT:
1) EVERYTHING IS GREY
ME3 discards the vibrant sci fi color pallete of ME1 and ME2,for grey and brown shades everywhere.Colors seem too washed out,too faded.
2) 6 ACTIONS ON THE SAME BUTTON ???
In ME2 we had Sprint,Cover,and Interaction all in the same button,and boy it was annoying some times.Well in ME3 we got all these functions PLUS side rolls and jumps all in the same button.
At a time I wanted to immediatly start running left to get to a distant cover spot,but Shepard did a short side roll instead,getting all the enemy's bullets in his face and dying.
Later on when I tried to activate a computer that was on top of a desk,Shepard wouldn't activate the damn thing but would instead duck and take cover behind the desk.I got in cover and out of it about 3-4 times until eventually I activated the computer because of luck.
3) STORY/DIALOGUE STUFF
So the available dialogue options given at all conversations where always 2 but from what I read people say that other dialogue options where cut from the demo for some reason.
The story while interesting,seemed to have a faster pace than it did in 2 past games which isn't of my like.In just a handful of minutes Reapers invaded,Shepard got re-recruited to the Alliance,and all the other things happened..
MEDIUM IMPORTANT:
1) ENEMIES SPAM GRENADES
So the enemies got a new attack,which is throwing grenades at you.And they do it when you are in cover to get you out of it.But getting out of it is slow and most of the times the time needed for the animation to happen takes longer than it takes the grenade to go boom. I felt like playing Battlefield 3 in third person.
2) MORE SCRIPTED EVENTS,NARROWER CORRIDORS
In ME1 spaces where very large and there where so many rooms you didn't had to visit for the main story,you could even get lost at times.In ME2 rooms became shorter so you could visit additional rooms that aren't important for the main story without getting lost.In this demo of ME3 it seems there are no additional rooms at all,and the actual shooting area became shorter and narrower than ever.It's too much straight forward "go there do that" to me,and I think it's bad there isn't enough to explore,'cause I liked exploration.
3) WEAPONS ARE UNBALANCED.
So check this out,an enemy needs like 10 or 15 bullets from the assault rifle to die,and it takes like 6-8 seconds to shoot them,while they die with about 5-6 pistol shots in less than 5 seconds.Makes the assault rifle feel unworthy in comparison to the pistol.
LESS IMPORTANT:
1) SHEPARD'S LIFE GOES DOWN FASTER
I played Mass Effect 3 single player,and I felt like I played Battlefield 3 multiplayer because Shepard's health seems to go down the same as fast. I played on medium difficulty and there where 2 enemies on screen.I thought of going out of cover to run to one of them that was distracted by Liara,and do the all powerfull melee attack to him.But before I even get to him I was killed down in like 2 seconds because the other guy killed me with 2 assault rifle bursts.
2) UNUSUAL GUN SOUNDS
The new gun sound doesn't sound like a lazer gun or a conventional gun either.It's just like the sound you would get by hammering a hammer to a piece of metal,too metallic.
3) CAN'T TALK TO SQUADMATES
So when I face at my squadmate,there isn't a circle appearing on them so I can't interact with them and have them say a line.It was a nice feature of past 2 games.
4) CAN'T HOLSTER WEAPON
There isn't a button to holster or unholster the weapon.