I had the time to try yersterday the prologue and the first mission (spoil : on Mars). The difference with the 2 other titles struck me. It was more mature and subtle, more intense atmosphere, less rubbish (ala hollywood, even if it is half wanted in that universe, it was sometimes a little too cheesy to my taste in the previous titles, especially ME2). A great, great opening, like in ME2. I just hope it does not turn less appealing like it was after the beginning in ME2, actually.
On the gameplay side, it is definitly a lot closer to ME2 than ME1. It is basically the very simple and working system used in ME2, but more complex and rich with improvements sometimes taken out of ME1. Skills are less minimalistic, weapons too (with something between the obnoxious ME1 inventory and the very flat ME2 inventory), and the cover system has been "improved" to something closer to Deus Ex 3 (with the possibility to jump between covers, etc), which makes the game a little harder to master btw. The AI, too, has gone under a lot of improvements. It behaves more like in DE 3, trying to catch you behind, moving behind their covers, throwing grenades at you to put you out of cover, etc. Also, when I saw the same difficulty options like in ME2 (easy, normal, veteran, hardcore and insane) I was like "ok, lets take hardcore directly, even veteran was too damn easy in ME2 and hardcore was quite enjoyable and not very difficult". Actually, it is a lot harder now. Not that enemies are especially lethal (though importing my old saves made me lvl 30 so maybe there is a little of this...), but they take AGES to take down. I mean, I am always emptying all my ammo before taking them down and sometimes have to go in melee to finish them off. It is funny but a little too much tough to my taste (1 or 2 rounds of ammo for a single NPC is... quite a lot). I am thinking to downgrade to veteran difficulty to try.