Apologies for length.
Combat: AI runs in front of you constantly, unless you tell them where to go. Hope that's still adjustable like it was in the first two games. Omni-blade is sexy and efficient! Also love the biotic melees! I can't wait to use it more when I get the third game! The environmental changes were excellent (blasts of Reaper cannons, smoke grenades, escaping varren, etc). I loved how no matter what class you pick, Shepard can now use all sorts of weapons--thank you! Rolling is quite fun and very useful, though I would likely have put it onto a different button, likely 'B'. Shepard doesn't seem to kneel down in cover until you press and hold 'A' (on Xbox).
Voice acting: It's too soon to tell what Mordin's replacement actor is going to be like, but all the other NPC squad mates were great as usual. I look forward to getting to know James Vega a whole lot better, great casting choice with Mr. Prinze Jr. Both Mr. Meer and Ms. Hale did very well as expected, although I am a bit biased towards the veteran (Hale's) interpretation.
Graphics/gameplay lighting: are great. Character creation screen should not use blue background--it's deceptive to the eyes. White is much more optimal. I much preferred ME2's character creation screen; the lighting was more adequate. Seeing as I'll be importing from ME2, this is a moot point, but for players new to ME who might like to focus on character customization, it's a bit of a let down.
Character customization: as stated previously, background should not be blue. But new hairstyles are oh so welcome! I also look forward to seeing how different female Shep's actions will act as opposed to male Shep in conversations, since that has been promised. That was a big peeve of mine in the previous games. (I.E., Female Shep in cutscene no romance before SM in ME2 would not necessarily crack knuckles as she looked at said picture but rather pick it up and run fingers along the edges of the frame or touch his/her face).
Music/scoring: Fantastic! Very dramatic and emotional!
Audio mix/SFX: Even after I adjusted the audio levels, there were quite a few instances where the 'underlying score' was mixed too hot, and I couldn't hear the cutscene dialogue. (I was wearing good headphones, too)! This is being a tad picky, but the assault rifle sounded too much like the automatic pistol.
RPG element: I'm thrilled to see the power trees back as promised, and they do indeed look very thorough. Although we didn't get too much story, that's quite understandable. However, I wish we could've gotten a little bit more of the story as to why Mordin (or replacement scientist if he died in the SM) was in a pod with the female krogan. He clearly has no weapon other than his omni-tool--I don't see how he could've protected her all that much. Why was Wrex piloting the shuttle, did the Alliance's pilot die? Also, there didn't seem to be all that different of NPC responses/consequences to the paragon/renegade choices in the dialogue. There should be an action, too. For instance, when Shepard is escaping earth and trying to get that kid out of the vents, when you select paragon, he/she should offer the hand like the game already does. If you select renegade, Shepard will say the other response AND try to grab the kid. Either way, the kid still makes the decision, and it still appears to be his choice. I like the helmet on/off options--that's a very nice touch. I could also be wrong, but I missed hearing unique dialogue from each squad member as either you or they made a headshot.
I'm also a little surprised as to why this was released so close to the game's launch. Improvements unfortunately cannot be made now 2 weeks before the game hits the shelves, so I guess…*sigh*…it's too late. All in all, though, if the release of this demo was just to attract a new market, hmm…problematic.
Overall, though, I was quite impressed. I already made my pre-order last month for the CE, and I hope that it'll be money worth spent!