I hate EA just as much as the next person, they buy up franchises I enjoy and destroy them. That said, in my personal experience, Origin has worked flawlessly as a content delivery system. I can't say the same for Steam. I also get faster DL rates with Origin.
I'll pre-order if only to get BF3 "free". After playing the demo I agree with many of the points already noted including the inconsistency of graphical detail and the forced, Gears of War style, cover combat.
I'm assuming you haven't played ME2? It was forced cover combat as well. From what I've seen in the demo, I'm pumped.
Improvements:
1. The addition of heavy melee. That omni-tool sword is ridiculously satisfying.
2. Enemy life bars have notches. Makes it a lot easier to detect the effectiveness of an attack.
3. Enemy AI is much improved all-around, especially in terms of tactics. Smoke grenades and bullet-proof shields provided an added challenge and greater variety to combat. The tactics are also no longer universal. The Reaper foot soldiers attack you head on, almost never taking cover, while the cerberus troopers take cover repeatably and attempt to flank while throwing grenades.
4. Cover is no longer perfectly safe. Some can be shot through, and if even a little bit of you is sticking out you'll take the occasional lucky shot.
5. Overall, the little tweaks to combat make it feel much more visceral and real than ME2 or ME1. In ME2 combat was often a simple puzzle with a reflex component. Here I felt like I was actually fighting.
6. The added abilities and ability upgrade tree mesh perfectly and add nuances to playstyle.
7. Ashely is smoking and the game is rated M for "partial nudity" (which ME1 was, but ME2 was not).
Disappointments:
1. Voice acting seems to have taken a hit. Most of it was alright, but more than a few lines sounded downright wooden. Granted ME has never been to Pixar levels, but even the voice acting in ME2 was more convincing. Maybe this is due to the cut-down nature of the demo, with added conversational material some of the out-of-place tonal inflections may make perfect sense.
2. Texture detail. I'm not picky. Plenty of graphics snobs here who will nitpick this point to death, but honestly I don't really care. I would prefer hi-res textures, but this is a console port. I imagine, much like ME2, a high-res texture mod will come out within a few months after release. If Bioware/EA is smart they'll offer it themselves, would be a fairly easy thing for them. But the graphics to me are passable, much like Pizza Hut is passable pizza and Guinness Draught is passable beer. In the high-action sequences you can't really tell anyway. It did not detract from the game's enjoyment for me.
3. At 1920x1200, the team-management and ability icons were overly small. I imagine this is a demo issue, as ME2 does not have this problem.