Huge World with well thought out terrain, diverse weaponry and spells, and tons of quests make this game worth playing.
I consider the voice acting in this game to be comic relief. As long as one starts playing this game in the right prospective, you'll continue playing it and find out why it carries such loyal fan base.
To follow-up on the above couple of sentences, the game does not have a very strong story line. You're a mercenary...plain and simple. For the most part, ignore the main quest, because it adds very little to the game. Mercenaries seek employment and are hired for: assassinations, extra army hand, covert ops, peace keepers, ...and maybe, even...to get a kitty out of a tree. (well, maybe not the kitty thing, but some very domestic tasks)
That's *really* the main thing you need to keep in mind when starting this game: you're playing as a mercenary and finding rather interesting quests abound.
The graphics aren't state of the art, but they aren't bad. Again, the world is huge. You encounter an extremely diverse assortment of monsters.
Once the enemies are killed, they will not respawn. Very interesting development decision they went with, that I like. This means that you can return to the areas, and not have to repetitively fight the same area again - leaving a bit more time for exploring. I'd recommend getting the resurrection spell, so you can resurrect enemies or creatures that *could* go extinct in your world if you kill them. (it'd be a sad world with everyone dead, ya know)
But, keep in mind, the world is densely populated. This gives you ample opportunity to use all of your various modded weaponry and powered up spells.
If you're an RPG fan, there really isn't much of a reason you should not enjoy this game.