I played through the marine campaign, and I enjoyed it. Those damn aliens do take a lot of punishment and at times you've only got your handgun, but you start to learn to rely on reflexes. An alien can strafe really fast for example and you really have to yank your gun left or right.
I did a bit of the predator-missions, and it's completely different. With the predator, it's no longer a corridor-shooter, but much more open world, coz you can jump onto a lot of places. I think it's a bit harder though, sometimes the distract-thing can't be used, and then it's really hard to take out a human. You really have to attack them in the back or wait for them to empty their clip.
I wouldn't say it's epic, but I probably would give it an 8. Just because the marine and predator gameplay is so different. Because as a marine, you are on edge. I'm not a fan of the close combat either, but how else should they have made it? It's allready quite difficult, aliens excel in close combat, but if they come to close, and you'd die instantly, the game would suck. If they do come close btw, your health will take a hit.
Graphics are quite nice. I'm running a HD 4890 now, at 1680x1050, with all settings maxed and as a Marine, I had no trouble keeping up 30 or more fps. There are only a few spots where it would actually get as low as 30fps. As a Predator, I get much lower scores with minima of around 15fps. I took this screenshot. The cave walls have a lot of detail, as do most things. Lighting looks good. I'm going to have to see how it runs on a HD 5870 with tesselation.