I probably spent more time hearing about Metal Gear Solid Online and having Metal Gear Solid Online tactics spoon-fed to me then I spent actually playing the game. But the single 6v6 match I did participate in was enough to give me a sense of whether I would like it or not: I sorta liked it.
The graphics are the best thing about the game, and I don't say that as some sort of backhanded compliment. The graphics really are quite good. The feel of the game was also well tuned. The movement and aiming, typical to most shooters, was tight but not too tight. It was a little weird aiming in a third-person view, especially without a reticule, but once I turned that on, it was fine. In fact, it wasn't something that I even noticed, which is the best thing you can say about controls, they should never get in the way of the experience. In the match I played each team of six started at opposite ends of a town. Not knowing the exact control set up, I wasn't sure how to do a couple of things, like hide or heal. But I did see fallen comrades getting fixed up and, so much better, a big cardboard box making it's way down an alley during a fire fight. The box would sit against the wall for a second, then lift up and sort of amble a bit forward, the feet of the guy hiding underneath painfully obvious. It was kind of funny, but in a good way.
The level we played was very well designed, filled with clutter and plenty of places you could hide, use to circle back behind people or snipe from. I wasn't thrilled with how you inflicted damage in the game. It didn't model the damage, that I could see, which is fine, but I think that made it hard to tell if you were really hurting the guy you were shooting at.
After getting picked off a couple of times, I switched to a shotgun. I ran to the roof of a building and waited for a team of two opponents to walk by beneath me and then jumped down behind them and unloaded with the shotgun. The lack of damage modelling made it hard to tell if I was hitting them and how close they were to death. So the moment wasn't nearly as satisfying as it could have been.
I think in the end the issue is that this game has the potential to attract fans of first-person shooters and a new audience of people who aren't fans of the MGS franchise, or perhaps not even aware of it. But when they drop into this game they're not going to be willing to give some of the game's oddities a pass. They won't be telling themselves that the single player games don't feature things like damage modelling or blood.
I don't think that's going to kill this game, not by any stretch, but there seems to be a little bit of a disconnect between the game's mechanics and the audience it might attract. That dissonance, for those not used to the game's peccadilloes, might end up preventing any substantive audience expansion I think.