The Combat Engine
The combat engine in Baldur's Gate, as in all other aspects of the game, is based on the AD&D rules, so your rate of fire and the chance of hitting the target are dependent on "dice rolls" which are handled by the computer. Bonuses and penalties for your attributes and weapons as well as the target creature's attributes and armor are taken into consideration also, as per AD&D rules. You should expect your characters to miss their target a lot, even if you're fighting with hand to hand weapons. This is normal and you can take heart that the enemies will whiff in their attacks on you at least as much.
The most interesting part though is that battles can be fought "real time" as in Diablo, or you can modify it to a pseudo turn based system. Remember the pause button we mentioned earlier? Pressing it during battle stops the action during which you can issue orders to your party members one by one. In this way you can have your mage ready a spell, have the archers target individual monsters, and have the heavily armored fighters protect the weaker members all at once. Press unpause and the actions are carried out again real time. The character AI is pretty decent and knows to keep attacking enemies until they're dead so you don't have to keep on clicking (your mouse will thank you for this; we've broken more than one mouse playing Diablo). After putting in many hours into playing the game (as Dennis and Kenn will attest, maybe too many working hours =p ), you'll learn to appreciate the ability to pause the game during battles. Trying to play it real time can be an exercise in frustration, because if you miss a click (very easy to do even if you're a real time gaming veteran) your character will walk up next to an enemy instead of shooting or attacking it. You can pretty much forget about getting spells ready in time or using potions in battle. There are configurable hotkeys but why stress yourself out when you can just pause?
Notice the colored lighting?
Besides the great combat interface, Baldur's Gate features an extremely interactive world. There are dozens of characters to talk to and interact with, and your responses can affect the plot and game play in big ways. What's interesting is that you're expected to act according to the personality alignment you chose in the game, or else there are consequences. If you picked to be a lawful good character for instance, then stealing money or killing innocent people cannot be part of your game plan. Another thing that we liked was the balance between plot and fighting. If there's not enough fighting or combat in a game, then things can get stale quickly but the converse is also true. If there's too much combat and not enough focus on the story, (like Final Fantasy VII and Diablo) then that can make the game boring also. With FF7 there's an inordinate amount of time spent running around just killing things to gain levels but you don't feel as much of a need to do what with this game. Baldur's Gate does a great job of balancing the two out; there's enough fighting to keep the game interesting, but not too much that you start to feel like you're losing focus on the plot and all your subquests.