Different, but fun!
As for gameplay and combat, each quest allows you to go through the mission your own way. If you love stealth games, this is definitely the game for you. But it also allows you to go through missions with guns blazing as well. The only complaint I have is that the game rewards you more if you do things more stealthy, which isn't really fair to players who love more action. But the game is still great if you just go through it shooting the bad guys out in the open. You also get to modify your character depending on how you play by adding "skill points" to certain skills. For example, if you like being stealthy, you could level up skills that would help with you being more stealthy, like the "invisibility cloak" which is very useful.
Weapons are great to. My only complaint about weaponry on this game is that you don't get much ammo, so use it wisely. You can also get weapon upgrades that make weapons MUCH better in missions.
This is a great game for fans of both RPG's and FPS's.