It's good, but you'd have to have played the previous MGS games to appreciate it. The story is pretty decent, but convoluted (as is typical of MGS). The gameplay is just merely ok. It suffers from the dev trying to do way too much with the controls, and quite frankly the gameplay suffers from it (its been that way since MGS3).
The online mode was pretty fun overall, but it was a godawful mess. The online mode isn't done through PSN, instead it's done through some proprietary konami portal in which you have to sign up for... and then you'll have to download some fairly large patches. In short, good multiplayer: horrible horrible horrible HORRIBLE execution.
Do I recommend the game? Yes with some qualifications. It's a great game, but you'd probably be better off playing the earlier installments first (MGS1 is $10 on PSN).