So here are my thoughts so far spoiler free. Like I've said before I'm not a super MGS fan but I'm not a hater either. The first and only MGS game was MGS2, I liked it for the graphics, and everyone gushed over the first one, so I was enjoying it until near the end when the story went all over the place.
So with MGS4 the first half hour is pretty much all cut scenes. There are moments where you take controll but you litterally walk 5 feet or do a simple action like crawl under a truck and then a new cut scene takes over. There are however some cool cutscenes near the beginning that appear to have nothing to do with the game, but I like them a lot and I hope I'll see more of those because they were totally unexpected.
So after the first half hour you can actually sneak around and play the game. This part of the game is kinda weak-sause so far. First the shooting controls aren't that great. "But santa this is a sneaking game?" You're right, but there are times when I mess up and the best course of action is just to shoot people, and compaired to the controls of any modern shooter, MGS controls suck. example, You have to hold the L1 button to draw your gun, then have to hit R2 to actually fire it, but if you want to make sure you're going hit people you need to hit the triangle button to go into first person perspective.
Another problem is that the enemies are just stupid. I walked around a corner and there were 2 dudes standing there and they start shooting me. I turn and run around two corners then pull out my weapon and wait for them to come around so I can shoot them all nice and propper, but they never came around the corner. I waited for a bit, then i noticed another way around and i went on my way. I think their idea of chasing me was to slowly walk after me.

Another time I see some guys from Army A shooting and dudes from Army B. I decide I would help Army B and shoot at A. I kill 2 out of the 3 but the third A guy just ignored me. He was looking right at me but didn't do any thing, i guess he was busy with other things. I'm hoping boss battles will save the combat for me but we'll see.
Then there's the online componet. First it had to load it, then there was a lengthy patch I had to download, then I had to create two different IDs (I'm sure some of you read all about it by now, luckily they open a browser in game to take care of that), then I had check my email to confirm my profiles, (you can't do this part in game, you either need to jump all the way to the PS3 startup screen or threw a computer, then I could play the game.
You get to make and avatar with a limited selection of parts. That's perfectly fine but say you decide you want to change the color of your pants or maybe your just tiered of that hat he's wearing. In order to do that you have to pay to make a new avatar. also you only get one free avatar per disk, so you have a siblings you need to share a profile.
There appears to be about 5 or 6 different modes but I just jumped into a simple team death match to get a feel for it, which in retrospect was probally a poor choice sense I hate the shooting controls away. If you couldn't guess by now I'm not a fan of the multiplayer. I might try out some of the other modes, but I'll just stick with the Bad company demo for now.
If I had to give it a score right now, I would probably would be floating in the 65-70 range-