Good customization and AI, annoying visual-novel story, lots of unlockables and extras. A Koei game worth the money.
Game play that is challenging all around, with some missions more difficult than others, enemies and allies that actually seem to have half a brain and more weaponry than Arnold Schwarzenegger in his entire career, and the fact that because enemies have minds of their own you can never play the same mission the same way twice.
However, most of the menu screens can be confusing to navigate at times, and the text-box story telling breaks up the immersion on a story that already borders on bananas at times, but the extras make up for that.
Speaking of, replay value is guaranteed because you can't unlock everything, including bonus missions and game modes, without going through all three mission paths, and even then there are still "secret parts" you have to collect in different missions to polish off the parts list.
I recommend that you try the game first, but if you can get interested, it's a handy time waster you'll have trouble putting down. Finally, a Koei game that's well worth the money.