I want to have this game's babies.
It really is Resident Evil 4 on steroids, and I'm perfectly fine with that.
About the only real downside, in my opinion, is not being able to use a Wiimote to aim. It was to be expected, but after RE4: Wii Edition, aiming with an analog stick just doesn't feel right. Believe me, you'll want to set the aiming speed to the fastest setting. Having said that, it is nice to have the option to adjust the speed of aiming, even if it only offers three settings (for now, anyway).
This game certainly has far more control options and variations than any of the previous games in the series. Even so, I really hope using A to run/reload and X for all of the context sensitive actions, including firing, is a Japanese-only thing. In the demo, there isn't any option to swap the two buttons, and it's the same for all four control types. I know other games' control schemes are backwards in Japan compared to here (see Metal Gear Solid), so I'm really hoping it'll be changed for the US release next year. Or if it isn't changed, at least allow the option to switch the buttons in the options menu.
As for the actual demo itself, it's great. It took me a few minutes to get used to the controls (mostly because of the A and X buttons), but once I settled back into the groove, I was popping off headshots with the greatest of ease. This is still very much Resident Evil, so the action, while no less intense than other games of its ilk, is inherently slower-paced. You still can't move and shoot at the same time, which is fine by me, but I know it will still bother quite a few people. The Gears-style controls work extremely well, however, and I may actually end up using it over the classic, RE4 controls (which are still an option).
The number of enemies has been upped considerably from RE4, and they're now a lot more aggressive than they were in that game. They also appear to be a bit tougher, too. It's hard to tell how much smarter they are, if at all, as the demo doesn't really offer a lot of opportunities for them to have to strategize or coordinate their attacks. Though if they keep coming at you in the full game like they do in the demo, they may not need to get the drop on you, as they can easily surround and overpower you without much difficulty.
Sheva is quite intelligent, leaps and bounds beyond your partner AI in the Outbreak games. She's smarter than Ashley in RE4, though she doesn't duck when you aim at her because there is no friendly fire in this game. Though I wouldn't be surprised if they gave you the option of turning friendly fire on or off, because when your partner is grabbed by an enemy, you can perform a melee attack to free them, or just shoot the enemy with your gun. The melee attack seems kind of pointless unless there's a possibility of hurting your partner from gunfire. That's just speculation on my part, though.
The amount of ammo seems comparable to RE4, except this time you're having to split it between two people, so you'll definitely have to be more careful about conserving ammo than you were in RE4 (though the PS2 and Wii versions had significantly less ammo than the GameCube version). Fortunately, there are all kinds of environmental hazards you can use against your enemies, and the variety and number of melee attacks you can perform have been largely expanded. Now you can perform melee attacks more often, such as when an enemy is lying on the ground, when you've shot them in the arm, or even after you've shaken them off. Some melee attacks can even be activated depending on your position in relation to the enemy (standing behind them, for example).
The graphics, needless to say, are incredible, but there are a lot of little touches that I personally really appreciate, like Chris looking down at an enemy while he (or she) is dissolving, or Chris and Sheva actually physically picking up ammo instead of going to a pause screen asking if you would like to pick it up or not. It's even actually pretty cool that you can dodge some enemy attacks by picking up an item off the ground at the right moment, sort of ducking out of the way. I also like that, if an enemy is carrying a glass bottle, you can shoot the bottle while they're holding it, causing it to shatter. They will then either proceed to attack you with the broken neck or drop it and pull out a new bottle.
The game has had brand new animations since TGS, but it's really nice to see them while actually playing the game for myself. There are only about two or three recycled animations from RE4 now, and they're really minor. But even though they're recycled, they've been touched up to flow more naturally and fluidly with the other animations. The physics have also been really tightened up. For example, if you shoot (or melee) an enemy, and it sends them flying backwards into a wall, they'll actually hit the wall and fall to the ground, and their animation will change to match the action. Previously, they would have just fallen back like normal with little to no recognition of coming into contact with a barrier.
A cute little Easter Egg of sorts I found is that you can actually make Chris taunt. I'm not sure if you can make Sheva taunt as well, but I imagine you can. You just have to click the right and left analog sticks at the same time. I wonder if this is purely superfluous, or if it will play into whatever Mercenaries-style minigame there will be in the final version. Maybe the taunt will boost your score or give you a time bonus or something (think Devil May Cry and how taunting raised your Style meter). I'm probably getting a bit too far ahead of myself there, though.
Oh, and since I made such a big deal about it before, you can steer your character while running using the Gears control scheme. You have two options for running. You can hold A and steer your character with the left analog stick, or you can click the left analog stick and steer with the right analog stick. I find the latter to be more comfortable.
That's about all I can really think of right now, but if I come up with anything else regarding the demo later on, I'll update this post.