Awesome Multiplayer, so-so single player.
First off I want to point out that i'm not really big on the Battlefield series and I only played Battlefield 2 (for PC and original Xbox) briefly. That being said I thought this game was great, specially the multiplayer aspect.
First off i'll start with the single player part of the game. Basically EA/D.I.C.E. I guess wanted to have a single player that was worth playing in the battlefield series in a way they succeeded and in a way they didn't. There is a story even though I found it to be kind of corny and dull. If your expecting a Gears of War or Halo epicness kind of story then you won't find it here. Basically your this new guy put into this team of trouble makers called "Bad Company" which the military puts them in the battlefield which a very low percentage of survival. The game is extremely linear and your pretty much just complete mission after mission. The team AI is extremely bad (or at least I thought so. There were times in the game we were around a tank for 2 minutes and I was out of rockets yet Haggard (the demolition expert in the team) didn't even try to shoot a rocket at it. This actually happens a lot and it makes you feel very frustrated especially in medium and hard difficulties. However one good thing is when you do respawn all the damage and enemies you done still exist so in theory you could just keep respawning and eventually beat the level/mission. The single player campaign will take you 6-8 hours to beat depending on what difficulty you play on. I played on Medium and I beat the campaign in 7 hours.
Now for the multiplayer aspect, the reason you probably bought this game. Its great. If theres anything they nailed right in this game its the multiplayer. The online multiplayer can hold up to 24 players which is a decent size for a console online game and most of the game I was in were around 20-24 players at most times. The ranking system is based off points (think Call of Duty 4) and even though its on a 1-25 leveling system (instead of the more common 1-50) its still very good. Theres are many awards like trophies which adds replayablility for the multiplayer. There are 5 classes that are very well balanced depending on what map you are playing and how you approach the enemy. When played online I hardly ever experienced lag. The only only negative part of the multiplayer is that they just have one gametype called Gold Rush in which you either protect your gold crates (you have a bunch of bases and two at each base) or attack the gold crates by shooting at them, shooting at them with a tank, or laying a explosive on it. To win you need to destroy all the gold crates if your attacking or deplete all the attacking teams respawns if your defending. This is a great gametype but it seems kind of limited there is only one gametype. EA has promised that Conquest would be available in a update after launch so that could add some variety to just the one gametype Gold Rush.
Overall the game is great. The single-player is somewhat decent and the multiplayer is great. If your looking for a great online multiplayer game that revolves around team work then you'll like Battlefield Bad Company.