Eh, first impression is kinda meh. I am sure the game gets better. I mean, the videogame press isn't so crooked that it would give something merely good such ejaculative reviews.
Right now, my primary concern is graphics. Halo HD was right. The only really significant upgrade the visuals have gotten, aside from stable HD resolution, is in the lighting model and in reflections. Overall, that's a pretty minor part of Halo, and totally not influential on gameplay. Having the opening level be a jungle emphasizes the lighting (and water effects), but when we get to "classic" Halo levels, like wide open outdoors on a planet, or in samey looking corridors, none of those upgrades matter. Also, there's absolutely no justifiable excuse for not having GOOD, like BULLSHOT QUALITY AA on this game. It's not jaggie or anything, but the lack of AA is noticeable.
Coming off of the year-old Gears a few days ago to this is a massive, massive downgrade. Couldn't Bungie get someone to help them out? It's basically the biggest game in the world, but you wouldn't know that by looking at it. It's not even in the same ballpark as Gears. Fuck, ballparks shouldn't even be mentioned in the same sentence as Halo 3 and Gears. Another fuck: for the environments it features, Resistance is at least as impressive visually.
Come on, Bungie, graphics are the EASIEST thing to get right, and they are 100% of what makes a first impression. Outta be ashamed.