First the good things...
The AI is greatly improved and a lot more challenging. Legendary first time around didn't really put you on the spot like it has done so far this time around. Rather than just running into you they do take cover, dodge grenades far quicker and they are just generally a lot smarter than they were in Halo. This for me on its own merit is worth a massive mention because the first Halo was just way too easy.
Secondly, the frame rate is smoother than last time and the general movement of the cross-hair is quicker. Aiming is more precise and the feel of the weapon/s is better than it was in the original.
Thirdly, Dual Wielding is a decent addition, picked it up instantly and didn't have a problem, really can't see where all the complaints are coming from with how difficult they are to use.
Fourthly, the new Assault Rifle is better than the original Assault Rifle, it now has a scope, is more powerful and in general it benefits those who prefer to go for head shots rather than all out warfare.
Finally it clearly takes awesome advantage of LIVE and I haven't even played it yet. The menus are excellent, the customisation is excellent, and the integration of LIVE 3.0 is excellent. From what I have seen of the LIVE aspects there has been some truly ground breaking stuff here for console online gaming.
But now the bad...
Firstly, it feels like an expansion pack and opening section was like the Pillar of Autumn all over again. The game handles the same, feels the same and even looks similar. I don't know what it is but I originally expected so much more. I am glad I toned it down with the hype.
Secondly the game doesn't visually blow you away, not like Doom 3 did and Far Cry or even Riddick. In all honesty I think that on face value Riddick is a better looking game and even the new physics engine hardly flatters. Doesn't bother me all that much but I'm just no-where near as impressed as I thought I would be.
Thirdly there feels to be something missing but I'm not sure what it is. The first area felt a little flat where as the opening section of Doom 3 had such an amazing atmosphere and a great feeling of tension. I will lay my finger on exactly what makes it feel a little empty as I progress.
I will play LIVE later after I have gotten on with some much needed work so I will add my opinions in here. For now though I just can't see it keeping me for even a minute away from Half-Life 2.
Of course MS want a Halo 3. $$$ on a rather large scale.
For this to happen, Bungie had to change the storyline, and flesh out the levels with some rather redundant levels. For example, the first Arbiter mission wasn't very necessary. Remember the advertising campaign: "Earth will never be the same"? Well, after Halo 2, not much has changed for Earth in the game, has it? Certainly not the full scale invasion the E3 demos, trailers and posters had us believe.
There's actually a thread on this on another forum which says a lot of this and more, apparently the guy who wrote it on the Bungie.net forums got banned for doing so.
As of yet the Plasma has eluded me.
But you could have been referring to the fact that NTSC = faster/better than PAL...