Icewind Dale is an exceedingly fun game.
It's graphics are good for the time, and spell effects still look cool. It offers tons of replay value because of the different choices; you will find that playing as a mage and playing as a fighter are two entirely different games.
It's difficulty is just right because, while you start out as a wimp vulnerable to bandits and most other enemies, you will grow into an uber-powerful hero. You also have very powerful spells at your disposal; this is balanced out by the fact that you can only use each spell once before you have to read your spellbook to remember it --- that's right, you forget your spells.
The voice acting is very good, some of the best I've heard in an RPG. The story is also good, but I'd rather not reveal anything.
This game is more combat oriented than Baldur's Gate; you'll be doing far more hacking than yacking.
All in all, Icewind Dale is a very good, if not the best, RPG.