Be warned. The game will crash your system as it stands.
However, as Black Ops 2 stands now, it's broken and since Activision put out a broken game, you should at least be warned about what you're getting.
During eight hours of play, not all at once but since launch, the game has froze my system five times. Two times within a half hour.
Now when the system reboots, you get that warning and I don't know about you, but I wonder, geez, I hope my system hasn't been bricked. So far, my system has rebooted but I have to wonder, if my system dies, what are the odds that Activision will cover the cost of a new harddrive for me.
I only got the game for multi-player and when it works, its pretty fun. Reminds me more of MW3 than the original Black Ops. It's nice to have new maps and weapons but I don't think I can say its better than MW3. The maps do a better job of preventing camping and that's a good thing.
What little I've played of the zombie mode has been disappointing. Certainly not as fun as the zombies in World at War or Black Ops. Maybe for me the whole zombie thing has worn thin and I found myself enjoying the survival mode of MW3 a lot more.
Without a doubt, patches will be released that will likely fix all freezing issues but as it stands now, the game will crash your system and you have to ask yourself, is one game worth my system? Wait and when the game is patched, check it out, I know I'm looking forward to it being fixed but until then, I'm just going to leave it in it's case and play NFS Most Wanted...
Addendum: It's late early Decmeber 2012 and the crashes seem to be under control. Reached level 42 and got bored of the game. The maps leave something to be desired. The hit detection also seems to be off. While it's initially fun to shoot guys who are off in the distance with only an assault rifle, it comes off as wonky and cheap after a while. I loaded up the original Black Ops and had more fun with that as the maps are more interesting and more of a challenge and when you shoot someone it feels like you've actually connected. Oh well, I knew at some point the COD games would take a nose dive. While Black Ops 2 isn't horrible, for multi-player fun, I can't recommend it over the original and MW3, both of which I find much more satisfying online games.